Multi-Select Improvements — Wartop Steam update #849425

Fixed some issues with picking up single dice Improved multi-select functionality. It should now be more accurate. If you click and drag from left to right you must full cover (the base) of terrain and models while picking them up. If you click and drag from right to left it'll do a partial select (e.g. a model that you draw the box in the middle of their base will be included in the selection). Fixed some other minor bugs and back-end logic.