Polish: update the RefCount API a bt and split Lock out

Polish: update the RefCount API a bt and split Lock out

* Shuffle RefCount.h and its unit-tests into src/base/

* Reworks struct Refcountable_  into class LockableObject in its own header
 + changing the reference counter accessors to a lock()/unlock() names
 + some minor symbol updates of code directly utilizing the RefCountable_
   members

With this we can begin the process of replacing our multiple different
implementations of the reference-counting pattern using LockableObject.

No code changes have been made. Just symbol polishing.

TODO: update the unit-tests for refcounting to use CPPUnit