Refactor/simplify the way we define and handle channel, cache and cache-container metrics

Defining metrics per resource via enums simplifies things immensely.
Also, some code cleanup:
* Use consistent class naming for resource definitions and add/remove/describe operation handlers.
* Eliminate superfluous static final values.
* Breakup CacheConfigOperationHandlers into individual add operation handlers for cache stores.
* Traverse model via resource paths where possible.
is this here just to support legacy map attribute properties and to convert it to sub resources?
if so it should be part of "backward compatibility" code and we should log a warning
and default behavior should not use it.