Cobra v1.33
Fixes bugs, most from last release.
- Tweak undefended derrick defenses to allow 1 blocking tile.
- Always default to HMG tower if returnDefenses() can't find any available defenses.
- Fix artillery personalities, and artillery groups in general, not attacking when no sensor units are available.
- Don't let base builders try to finish defenses outside the safe zone of 30 tiles from base.
- Produce sensors like before v1.32.