Update 1.3.0 Preview and Testing

I've uploaded a preview version of the upcoming 1.3.0 update to a Steam beta branch. This update adds a final batch of units and adds all the recently added units to campaigns. It also has a number of minor changes and fixes.

I haven't added VP modifiers for the new player vehicles nor any new player squad groups to the campaigns yet, but if you do want to test this update out, please switch to the preview beta branch. I don't anticipate any major crashes with this update, but as always if you find anything please let me know.

After further testing and final work on the campaigns I'll upload this to the main branch.