Allow the user to pick a player name for offline mode.
Big auth refactor. Now using session objects instead of the accounts themselves.
Sessions only last for one instance start and hold all the auth and player data.
* ProgressProvider now has an abort() call
* Abort button support added to the progress dialog
* YggdrasilTask and MojangAccount adapted to support abort
YggdrasilTask will time out after 10 seconds of no network activity, or when the user pushes the Play Offline button.
In offline mode, all instance update tasks are skipped! This will need further work.
* Adds support for listing all objects in an S3 bucket.
* Renames a bunch of network related classes (Download->Action)
* Net actions now have static constructors
