CDK-183	Schema creation and migration should validate that key fields of entity
schemas that belong to same table match

CDK-146	Validate that only one schema definition in a table has an occVersion
mapping

CDK-145	Enforce schemas that share a table don't clash in columns
The HBaseDatasetRepository now supports loading a dataset that is
a composite of multiple HBase datasets that share a table. Prior
to this, one had to create a dataset of the composite, but with
this change, creating a composite is now loaded at runtime (only
the sub entities need to be created).

The one downside to this is that the Dataset created now returns
a Map type instead of an entity that has member fields that make
up the composite type.