Support Private and Public applications

[judgej]

These have different configuration items and different algorithms.

[judgej]

• Private apps allow access to a single named organisation, do not expire, and do not require a callback URL. Great for developing an application against, as they can be developed from any location and on any type of hosting.
• Public apps allow authorisation against any organisation, which lasts for half an hour, but requires a single fixed callback URL. This is good for UAT or small production apps that do not need unattended access to an organisation.
• Partner apps allow access any organisation, and tokens can be continually renewed, so the app has unattended access once authorised. Up to three callback domains can be set up, so the callback is a lot more flexible. This flexibility comes at a higher price to provision as a higher level of trust is needed.

Private app support would be good next, for development.