don't try to spawn resources when the cell is already full

fixes #5699
Do not discard activity queue when FlyAttack completes. Fixes #4482.
Remove workaround for #4482 from 'Intervention' mission
Fix issue with capturing enemy buildings in 'Intervention' mission

The onDamaged event handler would still fire after an enemy building had
been captured. Fixed by checking the owner before starting repairs.

Thanks to Microbit for showing me that people actually did that.
Merge pull request #5711 from obrakmann/flyattack-fix

Fix FlyAttack discarding the activity queue upon completion
Merge pull request #5702 from Mailaender/reslayer-cell-full

Fixed exploding harvesters spawning resources on full cells