Add EffectDescriptor and associated collection to common elements

This patch adds EffectDescriptor and associated collection to common
policy pillar elements. It moves the code from the policy manager
and creates helpers function in the collection.

It also factorize the RoutingStrategy structure within a separated header
file.

Change-Id: I29964ff77564fadedf3237c8754240b21ae77297
Signed-off-by: François Gaffie <francois.gaffie@intel.com>