Audio Policy Refactor: reorganise headers inclusion

This patch reoganises the headers inclusion in order to prepare
the split of managerdefault into a manager and a separated lib
of pillar policy elements.

It also moves back the isStrategyActive to the manager to avoid
any dependancies from this pillars to the manager.

Change-Id: I1a35c45d86db7a3878a40dc7d6858dfea37c5ac9
Signed-off-by: François Gaffie <francois.gaffie@intel.com>