QCMetadata: add keys for audio sample bit width

Add key for audio sample bit width, used to pass
bit wdth info where media mime type is same.

Change-Id: I9681167dc0e227c6a0f3832e7c490e3b336de803

Conflicts:

	mm-core/inc/QCMetaData.h
QCMetadata: add key for pcm 24 bit

-Add 24 bit pcm key. This key is used by wav extractor to decide
the conversion of 24 bit input source to 16/8_24 format data.
-Add FLAC meta data specific keys

Change-Id: I9d0d40b5190aead29c4faf6cc433fcc4cfe8abef