[Bluetooth] Add BluetoothGATTServer{Service, Characteristic, Descriptor}

[Bluetooth] Add BluetoothGATTServer{Service, Characteristic, Descriptor}

This commit adds 3 interfaces, used to represent GATT objects exposed by
the local server.

[Verification] webapi-plugins build succeeds. Instantiating
tizen.bluetooth in Chrome Dev Tools succeeds.
The code will be further verified together with the code that
relies on it. Verification results will be reported in the next commits.

Change-Id: I8c5dd6a6da6d213518d0eb46d3bb0ca3e37b4629
Signed-off-by: Pawel Wasowski <p.wasowski2@samsung.com>