Get access tokens via oauth

[silsha]

An easy way to get the access token via oauth would be nice.

[tiefpunkt]

I would create a setup script that can do the "OAuth Dance" (I think that's the name). It should use predefined interfaces to the plugins. The setup scripts just wraps around those interfaces and lets you setup derptracker from the commandline. Later, we could integrate that functionality into a yet-to-be-created derp dashboard.