Switch between multiple games/timelines for players/GMs that are in multiple groups

[Gazook89]

Add ability to create and switch between multiple story timelines for those players who are in multiple games.

[Gazook89]

Functionally resolved by #10, which allows saving & downloading of all data as .json file, and importing it later back into localStorage. However, could likely make this more seamless by storing multiple games in localStorage at once and just switching back and forth entirely on the site. Only problem would be the possibility of running out of storage space, which is a current problem even now with only one game saved.