WTD-1051.
Add test cases for persistence cache to improve overall test coverage, WTD-672.
Add test case for cache to ensure the same object instance is given for multiple read calls, as this addresses WTD-791.
Move cache sources into their own bundle, for reuse with other persistence adapters; specifically supports the persistence adapter to the WARP Server, which is non-Couch but which will want to use this cache. WTD-702.
