Add bluetooth pairing agent

[Tim Curtis]

Worked perfectly to pair and authorize my iPhone :-)

Code:

pi@rp3:~ $ sudo /var/www/command/bt-agent.py --agent --disable_pair_mode_switch --pair_mode
ActivatePairMode called with inf
Agent registered
Agent registered as default agent.
Authorizing service (/org/bluez/hci0/dev_08_F6_9C_8F_6B_C5, 0000110d-0000-1000-8000-00805f9b34fb)

I'll integrate this into the UI for the next beta patch set so we can get some field testing.

-Tim