[Phoenix] Refactored Neutron-Auth implementation

[Andreas Wuest]

Hi

I've refactored the Neutron-Auth implementation. It is more generic, and 
notification of success or failure (even when user manually cancels the 
process) is now completely asynchronous via a passed in callback.

Please tell me if you experience problems with the new version. 
Basically, everything should work as before.

-- 
Kind regards,
Andi