I've added two commits. One that addresses [~sebersole]'s concern by moving to multiple maps and decoupling the region concept from the `Region` object. One that addresses Radim Vansa's concern by moving CDD validation in to the `TransactionalDataRegion`.

Regarding your second point in the comment above Steve, I think my overloaded `get[Type]Region` methods have caused the confusion. The `get[Type]Region(String name)` methods return null, but they were existing public methods. The new methods are `get[Type]Region(String name, CacheDataDescription cdd)` and they throw (or rather threw at this point with the new commits) exceptions on collisions.