Support schema in RemoteDatabase interface

[lvca]

The RemoteDatabase class mimics the EmbeddedDatabase interface for remote operations. The most common API has been implemented, but the schema is missing and the user has to use SQL to achieve manipulation of the schema.

[lvca]

Basic remote schema class done. DocumentType, VertexType and EdgeType should be interfaces.

[lvca]

Completed. The most used methods are now in the remote schema, so switching from Embedded to remote should be painless.

[lvca]

I had to generate interfaces for DocumentType, VertexType, EdgeType, and Property with 2 implementations: embedded and remote.