Removed UnitCollection

Replaced with helper functions
Worked on better defense decisions
Messages when worker or structure is under attack
Quick commit
Working on defense decisions
Crashes occasionally
Still working on new defense strategy
Added stim packs to marines
Merge branch 'squad-2' of github.com:rarosu/FnulAI into stim
Added stim pack support

Marines and firebats now use stim packs when all criteria are satisfied.
Those criteria are:
- An enemy is within weapon range
- The squad they're in has at least one medic
- They are not currently affected by a stim pack
Must fix response squad erase
Merge branch 'stim' of github.com:rarosu/FnulAI into squad-2
Forgot a semi-colon
Basic defensive strategy working
Merge branch 'stim' of github.com:rarosu/FnulAI
Siege Tanks almost working

Something wrong with isThreatened
Siege Tanks working fairly well
Merge branch 'squad-2'