[Bluetooth] Device discoverable test

Issue #664

This test:
- enables bluetooth on the device
- sets the device's bluetooth name
- turns on the device's bluetooth discoverable mode
- uses the host machine's bluetooth controller to perform an inquiry and verify device is visible
- turns off the device's bluetooth discoverable mode
- uses the host machine's bluetooth controller to perform an inquiry and verify device is no longer visible
- disables bluetooth on the device

To run this test, a python module called 'PyBluez' [1] is used to interact with the host-side bluetooth adaptor. The PyBluez module must be installed on the test machine.

[1] http://code.google.com/p/pybluez/wiki/Documentation