Currently a base type can be configured for a service in the backend config file. This story is to expand that support to allow more than one base type be specified in the config file. 

Where the base types are read (ElementOperation getBaseTypes()), it shall be checked if the base types exist for the given model. Where a base type does not exist for that model it shall be ignored.

This will allow us to use different base types for the same service category where it is used for different models