Simplified meta data model for cloud connectors

Modified ConnectorMetaDataEnabled interface to facilitate caching of MetaData in Studio. Added parentNames to PojoMetaDataModel so allow hierarchies of POJO types to allow multiple pojos to be substituable for a given pojo model.

Changed ConnectorMetaDataEnabled to work with metadata about metadata (aka MetaDataKey). Added SimpleMetaDataModel for a lighterweight pojo option. Added toString() methods.

Added hashcode and equals methods

Added method for getting artifacts for Message Processors. Also a couple bug fixes.

Added toString method

Renamed MetaDataEnabled to OperationMetaDataEnabled to eliminate confusion with ConnectorMetaDataEnabled