[Bluetooth] BLEAdapter isScanning and BLEDevice new functions.

[Bluetooth] BLEAdapter isScanning and BLEDevice new functions.

[ACR] TWDAPI-264

Bluetooth module can be upgraded with these functions provided by native layer:
BluetoothLEAdapter
bool isScanning ()

BluetoothLEDevice
bool isConnected ()
unsigned long getAttMtu ()
void requestAttMtuChange (unsigned long newAttMtu)
long addAttMtuChangeListener (ConnectionMTUCallback callback)
void removeAttMtuChangeListener (long watchId)

[Verification] New functionality has been tested on TW2 device in
developer console.

Change-Id: Id5f56ee4d67591b6d917552c6b7a09d2a5a06386
Signed-off-by: Arkadiusz Pietraszek <a.pietraszek@samsung.com>