aaa: Changes to ExtensionsManager

The following changes are introduced:

1. ExtensionsManager is no longer singleton.
2. For engine related modules - EngineExtensionsManager is a singleton wrapper.
that also initilizes ExtensionsManager with the proper application name.
3. Splitting load to loading the extension and activating it.

Change-Id: I1c914df29a0dbf52ff6d2f8149687b31b4faffe1
topic: AAA
Signed-off-by: Yair Zaslavsky <yzaslavs@redhat.com>