BluetoothHeadset.java:

Added ACTION_VENDOR_SPECIFIC_HEADSET_EVENT,
EXTRA_VENDOR_SPECIFIC_HEADSET_EVENT_CMD,  EXTRA_VENDOR_SPECIFIC_HEADSET_EVENT_ARGS.

BluetoothAssignedNumbers.java (new file):
A home for BT assigned numbers, beginning with the company IDs.

HeadsetBase.java:
Reformatted some code.

AtCommandHandler.java:
Fixed comment typos.

Change-Id: I34d6f248166305d72be66632779fc963b894379c

Added EXTRA_VENDOR_SPECIFIC_HEADSET_EVENT_COMPANY_ID.
Fixed a minor comment typo.

Change-Id: I8550692c13510a853c894b2d108bef4520d931c2