Fixed MAJOR bug that deletes original data upon first load with mod

Now With Singleplayer!

Number with up and down arrows added to the title screen beside the main menu, changing the number that corresponds to the current account. Account selection applies to all singleplayer worlds.

• "/account" command available to other players when hosting a LAN world; no limit on max accounts in LAN.

• Each player on a server can now be given separate max account values in multicount.properties.

• "command" setting added to multicount.properties enabling the "/accountmax" op-only command (off by default).

• "/accountmax [maxCount] <targets>" command is used to easily set the maximum allowed accounts.

• Added "/accountmax query <targets>" (always on) command for ops to display the maximum accounts for each target.

• Display the current account being used by running "/account" standalone.

• Other accounts now saved as [uuid].dat[account number] instead of [uuid].dat[account number - 1].

• Completely reworked backend.