Avoid forcing engine_conf to a dict

It is valid to provide engine_conf that is None and
when a engine is loaded it will notice that it is None
and load its default configuration.

Change-Id: Icde7ac85921f3b434cee39a9dfe7de997f2120bf
Increase the level of usefulness of the dispatching logging

Change-Id: Ief62a3436aa7fe86c98e026ec5522d2f5e2aa29f
Move flattening to the action engine compiler

Since flattening is only one way to compile a flow and
nested flows and atoms into a compilation unit move this
functionality into the engine module where it is used.

Change-Id: Ifea6b56cf5f2a9c1d16acabfaae6f28aeb6534a0
Merge "Move flattening to the action engine compiler"
Invert the conductor stop() returned result

Instead of returning whether the conductor is still dispatching
return whether the stop was successful or whether it was not. This
matches better with the expected semantics of the stop routine.

Change-Id: Iccdca017e174adbd8eb3c093c6d0ea0c570792f5
Merge "Avoid forcing engine_conf to a dict"
Merge "Increase the level of usefulness of the dispatching logging"
Merge "Invert the conductor stop() returned result"