[Ci-users] duffy requests

1) Public source code
2) Arbitrary metadata (could be JSON or just a blob) like /Node/get/?key=blah&metadata=<base64 encoded json>
   Then a new /InventoryExt verb that returns JSON like:

[
    { "name": "n49.pufty", "ssid": "abcde", "metadata": "<base64 encoded json>" },
    { "name": "a29.pufty", "ssid": "abcde", "metadata": "<base64 encoded json>" }
]

3) Also add a new option to /get/  named "longpoll" which means the machine is automatically deallocated when the requester's TCP connection closes.  This would help ensure that e.g. cancelling the job or a Jenkins restart etc. automatically deallocated the machine