Let the TheaterCommander manage front line stance.

This improves the AI behavior by choosing the stances non-randomly:

* Breakthrough will be used if the base is expected to be capturable and
  the coalition outnumbers the enemy by 20%.
* Elimination will be used if the coalition has at least as many units
  as the enemy.
* Defensive will be used if the coalition has at least half as many
  units as the enemy.
* Retreat will be used if the coalition is significantly outnumbers.

This also exposes the option to the player.

game/theater/controlpoint.py

@@ -271,6 +271,9 @@ class ControlPointStatus(IntEnum):
 
 
 class ControlPoint(MissionTarget, ABC):
+    # Not sure what distance DCS uses, but assuming it's about 2NM since that's roughly
+    # the distance of the circle on the map.
+    CAPTURE_DISTANCE = nautical_miles(2)
 
     position = None  # type: Point
     name = None  # type: str
@@ -727,6 +730,10 @@ class ControlPoint(MissionTarget, ABC):
 
         return self.captured != other.captured
 
+    @property
+    def deployable_front_line_units(self) -> int:
+        return min(self.frontline_unit_count_limit, self.base.total_armor)
+
     @property
     def frontline_unit_count_limit(self) -> int:
         return (