audio policy manager: more generic A2DP impl.

audio policy manager: more generic A2DP impl.

This change makes support for A2DP related audio policy more generic:
-removed WITH_A2DP compilation switch
-use output profile descriptors listing the parameters
(sampling rate, format...) devices and attributes (low power, tunneling...)
for each available output.
All the behavior specific to A2DP is derived from the A2DP output profile
descriptor.
- removed obsolete a2dpUsedForSonification() method.

This is a first step towards a more generic support for different audio
hardware modules (USB, HDMI) and output streams supporting different
combinations of parameters (sampling rate, format...) and attributes
(low power, tunneling...).
Ultimately, the hw modules and output descriptors will loaded from a
configuration file.

Change-Id: Ife3e49e1afbcb72613bfc8ce38919bb087ca85ea