FeedMe table manage feeds + fix warning addFeed (#3075)

FeedMe is able to add/remove subscriptions.

Fix minor bug introduced by
https://github.com/FreshRSS/FreshRSS/pull/1731
If the category ID is provided, we must first search for the existing
category before trying to add a category with the provided name.
Fix:

```
SQL error addCategory: ["23000",19,"UNIQUE constraint failed:
category.name"]
```

README.fr.md

@@ -179,7 +179,7 @@ et [l’API Fever](https://freshrss.github.io/FreshRSS/fr/users/06_Fever_API.htm
 | App                                                                                   | Plateforme  | Logiciel libre                                                | Maintenu & Dévelopé    | API              | Mode hors-ligne | Sync rapide | Récupère plus d’articles dans les vues individuelles | Rrécupère les articles lus | Favoris  | Étiquettes | Podcasts | Gestion des flux |
 |:--------------------------------------------------------------------------------------|:-----------:|:-------------------------------------------------------------:|:----------------------:|:----------------:|:-------------:|:---------:|:------------------------------:|:-------------------:|:----------:|:------:|:--------:|:------------:|
 | [News+](https://play.google.com/store/apps/details?id=com.noinnion.android.newsplus) with [Google Reader extension](https://play.google.com/store/apps/details?id=com.noinnion.android.newsplus.extension.google_reader) | Android | [Partially](https://github.com/noinnion/newsplus/blob/master/extensions/GoogleReaderCloneExtension/src/com/noinnion/android/newsplus/extension/google_reader/) | 2015       | GReader | ✔️             | ⭐⭐⭐       | ✔️                    | ✔️                 | ✔️         | ✔️     | ✔️       | ✔️           |
-| [FeedMe](https://play.google.com/store/apps/details?id=com.seazon.feedme)             | Android     | ➖                                                            | ✔️✔️                   | GReader          | ✔️            | ⭐⭐        | ➖                             | ➖                  | ✔️         | ✓     | ✔️       | ➖           |
+| [FeedMe](https://play.google.com/store/apps/details?id=com.seazon.feedme)             | Android     | ➖                                                            | ✔️✔️                   | GReader          | ✔️            | ⭐⭐        | ➖                             | ➖                  | ✔️         | ✓     | ✔️       | ✔️           |
 | [EasyRSS](https://github.com/Alkarex/EasyRSS)                                         | Android     | [✔️](https://github.com/Alkarex/EasyRSS)                      | ✔️                     | GReader          | Bug           | ⭐⭐        | ➖                             | ➖                  | ✔️         | ➖     | ➖       | ➖           |
 | [Readrops](https://github.com/readrops/Readrops)                                      | Android     | [✔️](https://github.com/readrops/Readrops)                    | ✔️✔️                   | GReader          | ✔️            | ⭐⭐⭐       | ➖                             | ➖                  | ➖         | ➖     | ➖       | ✔️           |
 | [Readably](https://play.google.com/store/apps/details?id=com.isaiasmatewos.readably)  | Android     | ➖                                                            | ✔️✔️                   | Fever            | ✔️            | ⭐         | ➖                             | ➖                  | ✔️         | ➖     | ➖       | ➖           |

README.md

@@ -102,7 +102,7 @@ and [Fever API](https://freshrss.github.io/FreshRSS/en/users/06_Fever_API.html)
 | App                                                                                   | Platform    | Free Software                                                 | Maintained & Developed | API              | Works offline | Fast sync | Fetch more in individual views | Fetch read articles | Favourites | Labels | Podcasts | Manage feeds |
 |:--------------------------------------------------------------------------------------|:-----------:|:-------------------------------------------------------------:|:----------------------:|:----------------:|:-------------:|:---------:|:------------------------------:|:-------------------:|:----------:|:------:|:--------:|:------------:|
 | [News+](https://play.google.com/store/apps/details?id=com.noinnion.android.newsplus) with [Google Reader extension](https://play.google.com/store/apps/details?id=com.noinnion.android.newsplus.extension.google_reader) | Android | [Partially](https://github.com/noinnion/newsplus/blob/master/extensions/GoogleReaderCloneExtension/src/com/noinnion/android/newsplus/extension/google_reader/) | 2015       | GReader | ✔️             | ⭐⭐⭐       | ✔️                    | ✔️                 | ✔️         | ✔️     | ✔️       | ✔️           |
-| [FeedMe](https://play.google.com/store/apps/details?id=com.seazon.feedme)             | Android     | ➖                                                            | ✔️✔️                   | GReader          | ✔️            | ⭐⭐        | ➖                             | ➖                  | ✔️         | ✓     | ✔️       | ➖           |
+| [FeedMe](https://play.google.com/store/apps/details?id=com.seazon.feedme)             | Android     | ➖                                                            | ✔️✔️                   | GReader          | ✔️            | ⭐⭐        | ➖                             | ➖                  | ✔️         | ✓     | ✔️       | ✔️           |
 | [EasyRSS](https://github.com/Alkarex/EasyRSS)                                         | Android     | [✔️](https://github.com/Alkarex/EasyRSS)                      | ✔️                     | GReader          | Bug           | ⭐⭐        | ➖                             | ➖                  | ✔️         | ➖     | ➖       | ➖           |
 | [Readrops](https://github.com/readrops/Readrops)                                      | Android     | [✔️](https://github.com/readrops/Readrops)                    | ✔️✔️                   | GReader          | ✔️            | ⭐⭐⭐       | ➖                             | ➖                  | ➖         | ➖     | ➖       | ✔️           |
 | [Readably](https://play.google.com/store/apps/details?id=com.isaiasmatewos.readably)  | Android     | ➖                                                            | ✔️✔️                   | Fever            | ✔️            | ⭐         | ➖                             | ➖                  | ✔️         | ➖     | ➖       | ➖           |

app/Controllers/feedController.php

@@ -54,11 +54,12 @@ class FreshRSS_feed_Controller extends Minz_ActionController {
 		}
 
 		$cat = null;
-		if ($new_cat_name != '') {
+		if ($cat_id > 0) {
+			$cat = $catDAO->searchById($cat_id);
+		}
+		if ($cat == null && $new_cat_name != '') {
 			$new_cat_id = $catDAO->addCategory(array('name' => $new_cat_name));
 			$cat_id = $new_cat_id > 0 ? $new_cat_id : $cat_id;
-		}
-		if ($cat_id > 0) {
 			$cat = $catDAO->searchById($cat_id);
 		}
 		if ($cat == null) {