Remove Versionable from SchemaBase

SchemaBase extends Versionable, and as a result an update via syn.store() of a View or Table will lead to a versioned PUT, e.g.

But the backend is just discarding the version as described in https://sagebionetworks.jira.com/browse/PLFM-5702 and as discovered again in https://sagebionetworks.jira.com/browse/PLFM-6362

Removing Versionable doesn't cause any obvious immediate issues in tests, this issue tracks that we ensure that it can be safely removed.