Documentation: add etcd-rest to libraries-and-tools.md

Add link to the etcd-rest client under the 'Java libraries' sub-section.

Fixes #4906

Documentation/libraries-and-tools.md

@@ -27,6 +27,7 @@
 - [diwakergupta/jetcd](https://github.com/diwakergupta/jetcd) - Supports v2
 - [jurmous/etcd4j](https://github.com/jurmous/etcd4j) - Supports v2, Async/Sync, waits and SSL
 - [AdoHe/etcd4j](http://github.com/AdoHe/etcd4j) - Supports v2 (enhance for real production cluster)
+- [cdancy/etcd-rest](https://github.com/cdancy/etcd-rest) - Uses jclouds to provide a complete implementation of v2 API.
 
 **Python libraries**