Add a link to filter categories

In the category configuration page, I added a filter link on each category. It works the same way than the "filter" link on the feed configuration page.

See #514

app/views/configure/categorize.phtml

@@ -18,6 +18,9 @@
 					<input type="text" id="cat_<?php echo $cat->id (); ?>" name="categories[]" value="<?php echo $cat->name (); ?>" />
 
 					<?php if ($cat->nbFeed () > 0) { ?>
+					<a class="btn" href="<?php echo _url('index', 'index', 'get', 'c_' . $cat->id ()); ?>">
+						<?php echo _i('link'); ?>
+					</a>
 					<button type="submit" class="btn btn-attention confirm" formaction="<?php echo _url ('feed', 'delete', 'id', $cat->id (), 'type', 'category'); ?>"><?php echo Minz_Translate::t ('ask_empty'); ?></button>
 					<?php } ?>
 				</div>