Fix a lack of difficulty dropdown yaml in other mods (d2k/cnc) causing crashes
Fix mechanic being able to repair infantry. Adjust mechanic repair damage from 20 to 10
Change mech hotkey to c
Make oil derricks repairable by engineers
add classic left-click orders
improve the classic mouse behaivor

- don't require to deselect units to change selection
- fix issue with broken building placement on right-click orders
- don't select enemy units when left-click attacking
- build palette won't interfere with unit orders anymore
let Chronotank/Minelayer accept left-click-orders
pull mouse button preference from global property