Fixed query builder for cross-database relationships

You should now be able to create relationships across database types, from native Model classes to FMModel classes. Check the updated docs for instructions.

Added script param as optional second param

Added script param as optional second parameter in script() query call as an alternative to having to chain scriptParam()

Relationship and container improvements

• Fixes for relationships returning too many records.
• Containers now automatically detected - no longer need to declare in model.