Change replay to serverside

This moves the replay playing code serverside, also allows loading from replay.

TODO:
 - Support Multiplayer loading
 - Change Replay browser to use the server system
 - Allow to change players between saves.
 - ~~Move the load button in the lobby so it doesnt cover the options button.~~

This superseeds #6238 completly except you currently cant watch replays of loaded games,
this will be fixed as soon as I move the replay watching to the new system.