Implement optional interfaces
- Purge
- PutStream
- Copy
- Move
- DirMove
- DirCacheFlush
- ChangeNotify
- About
Make Hashes() return the intersection of all the hashes supported by the remotes
* Fix error handling in List and NewObject
* Fix Precision in case we have precision > time.Second
* Fix Features - all binary features are possible
* Fix integration tests using new test facilities