Draft: Dimensional synching

This merge request adds dimensional synching through an 8-bit unsigned integer that gets sent when the player's ticcmd_t structure gets built. However, it is marked as a draft as I got to rewrite some code to fix a bug since the dimensional synching needs to be done on the player's side.

New variables: player.dimension: this variable determines the real synching dimension that the player is located in and can be freely modified. player.cmd.dimension: this variable is set to the value of player.dimension during the construction of the player's ticcmd_t structure so that the player's dimension can be properly synched during consistancy checking.