Changes for API of Bluetooth Discoverability. DO NOT MERGE

1. Apps can ask for any time between 0 and 3600 secs
2. O implies always discoverable
3. Any invalid values will default to the default - 120 secs.
A dialog is shown by the system to the users to accept the change
in discoverability values.

Change-Id: I34ebd907656a87508b0f0b1a4bce78134edcaebf