Move SQLBlob and Binary classes outside of VCS

The classes SQLBlob, Binary, BinaryManager, etc. are part of VCS but will need to be reused and available for other storages like MongoDB.

So the classes should be moved to another bundle, nuxeo-core-storage.

SQLBlob is not about SQL so should be renamed StorageBlob. A compatibility interface SQLBlob will be kept for a while because we have some code doing instanceof checks and calling getBinary.