Neutron Refactoring

v2_0 -> v2
No options (redesign)
More features (extension-related)
Some bugfixes
May [Unwrap](https://github.com/jclouds/jclouds/blob/master/core/src/main/java/org/jclouds/rest/annotations/Unwrap.java) or [SelectJson](https://github.com/jclouds/jclouds/blob/master/core/src/main/java/org/jclouds/rest/annotations/SelectJson.java) work?