Unhide Bluetooth Low Energy public APIs

Updated API headers. Add BluetoothManager to be retrieved by
context.getSystemService(Context.BLUETOOTH_SERVICE).
LE scan functions are placed in BluetoothAdapter
The GATT API are device driven instead of a profile-driver.
bug 8450158

Change-Id: I424a4cedaac3ef8120a05996500008dd210d2553