Fixes for rails: Allow UUID/JSONB column types, ensure anonymous_class is defined

[tonyhb]

• Check for anonymous_class definition before attempting to use it
• Ensure UUID column types are mapped to strings when using UUID PKs.
• Add JSONB -> %jsobn type mapping.

The only thing I'm uncertain of is JSONB type mapping. As it's JSONB this should be parsed; the resulting datatype could be any primitive matching String or Integer or Float or Hash or Array or %bool. I've added a type map for %jsonb, though I'm not sure if this is correct.