[WFCORE-60] Add a registry for capabilities and requirements, modifiable via the OperationContext
[WFCORE-60] Add convenience ops to base add/remove handlers
[WFCORE-60] Add ability to register needed capabilities to the subsystem test infrastructure
[WFCORE-60] Remove 'getDescription' from the capability API until we clarify its use
Merge pull request #128 from bstansberry/cap-req

[WFCORE-60] Runtime capabilities and requirements