Virtualizer: replace device type by virtualization mode

Define audio virtualization modes that represent the different
 audio processing modes.
Change and document the change in the methods used to describe
 the virtualizer capabilities and characteristics.
Implement internal conversion functions between virtualization
 modes and device types.

Bug 17059703

Change-Id: Ic4db211d6f51492be9088783246abb4b2866d76f