audio policy: use new audio device representation

Represent audio devices with more attributes than just the
type (audio_device_t).
This is in preparation for new routing APIs allowing
device selection based on more criteria than just the type
(address, channel mask...)
A new class DeviceDescriptor is created and used by functions
needing more information than just the device type.
Bit fields for available and supported input or output devices are
replaced by vectors of device descriptors.
Each available device is allocated a unique ID for future use.
Removed obsolete mA2dpDeviceAddress, mScoDeviceAddress and mUsbCardAndDevice
fields replaced by address stored in DeviceDescriptor.

Policy decisions like getDeviceForStrategy() are still based
only on the device type.

Change-Id: I5de3b3ffb12ff8dcfb746782ab1e6b15bf040d0c