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.
* Corrected an uninitialized variable that prevented forge list loadinf on Windows
* Run the update step twice for FTB instances to ensure forge libs get downloaded
* Do not re-create on every reload
* Use the version.json/custom.json logic properly
* Should be offline-friendly
* FTB instances can be copied, turn into normal instances
