Update 0.3.23 - Minor bugfix

This is a small patch - it does add some progress on mars, but you cannot access it without cheats (and doing so is a bad idea, it might cause problems with your save later).

Changelog

• Added elemental damage system (same as original Aground). It'll be used for elemental spellbooks later, and mods can use it now.
  
• Added toggle all option to select structure window (com station/device)
  
• Fixed a splitscreen controls bug, and a few other minor fixes.