Added Sheepdog distributed file system

Added Sheepdog, which is a already mature distributed block storage, S3 Storage and distributed file systems. Created by the japanese NTT and licenced as GPL2.

README.md

@@ -284,6 +284,7 @@
   * [OpenAFS](http://www.openafs.org/) - Distributed network file system with read-only replicas and multi-OS support.
   * [Ori Filesystem](http://ori.scs.stanford.edu/) - A Secure Distributed File System built for offline operation.
   * [Swift](http://docs.openstack.org/developer/swift/) - A highly available, distributed, eventually consistent object/blob store.
+  * [SheepDog](https://sheepdog.github.io/sheepdog/) - A distributed Blockdevice, Rest, QEMU and distributed Filesystem storage.
   * [TahoeLAFS](https://tahoe-lafs.org/trac/tahoe-lafs) - secure, decentralized, fault-tolerant, peer-to-peer distributed data store and distributed file system.
   * [XtreemFS](http://www.xtreemfs.org/) - XtreemFS is a fault-tolerant distributed file system for all storage needs.