Bluetooth discoverable test, associated host-side class

Conflicts:

	gaiatest/atoms/gaia_data_layer.js
Move host-side code to bluetooth utils
Bluetooth discoverable test
Updates as per review; also use common methods in pull 600
Change common method names to same format as others, verify when bt enabled/disabled
Fixes for using methods in pull 600
Post-review updates
Final post-review changes
Add a requirements.txt file to specify the package needed for the bluetooth test
Add manifest file for bluetooth tests