Issue #41: Initial cut of cache event listener notification layer and relevant plumbing, though no actual events are wired in yet.
Issue #41: added event factory methods and store-initiated event support (expiration/eviction).
Issue #41: wired in the rest of cache events and added unit tests.
Issue #41: incorporated PR comments
Merge pull request #169 from vfunshteyn/issue-41

Issue 41 - cache events