configurable blacklist zones
delete ai units before next mission starts

currently only dead ai are cleaned up
this adds a flag to the spawn script to identify the mission type they
are associated with. once a mission starts, all the units associated
with the previous mission of that type are purged using epoch cleanup
code.

buildings/etc could also be added into this.
fix issue with missing semicolons in EM1
more reliable ai killed cleanup timer
Merge remote-tracking branch 'origin/clean-units' into merge
Merge remote-tracking branch 'origin/ai-killed-timer-fix' into merge