Multiplayer/merged saves

A new type of game mode selected upon starting a new save: Collaborative Multiplayer.

Basically, in this mode, the first time the sandbox is saved it is also uploaded to the player's Simple Rockets 2 profile. During upload a password/shared key is made as well.

Then, when this same sandbox is saved again, the game asks for this password/shared key and updates the original sandbox's FlightState.xml and craft-#.xml files, so that other players who have downloaded this sandbox, receive updates to the sandbox (like updates to planetary systems when making a new save from a downloaded system)

The password/shared key allows the player to let other players update the original submission when they save the sandbox with the correct password. Otherwise incorrect/no passwords just save locally.