Making BatchCache a singleton and added test-access to set in builder
Moving base test classes to their own package
Moving phoenix covered indexing stuff to index-core.

This just makes it easier to test for the moment. We might move it back, might move
the covered index stuff to use the Phoenix-builder stuff instead.
Adding basic end-to-end test + bug fixes.

Main change: remove row/batch caching. Decided it wasn't needed, in favor of using the HBase block cache.
Other: minor nits in initialization of objects, etc.