[WIP] Refactor chef finder methods into a single module

Refactor the chef finders into a single module, then include them into *Objects.

This can help in debugging and profiling the chef queries, and keeps the syntax consistent across the *Object classes.

The existing methods were covered by tests (https://github.com/crowbar/barclamp-crowbar/pull/1041), to ensure the API won't change. Also, they now emit a deprecation warning to help in transitioning to the new syntax.

The patch set is currently not field tested, which is why its marked WIP.