This limit is determined by the number of buildings that belong to Ammo
Depots at the front line's connected Control Point. The limit increases
for every surviving building at ammo depot objectives.
There is a lower limit to the number of units that will spawn, so that
if there are no surviving ammo depot buildings at a control point, there
will still be some ground conflict.
This also removes the "factory" type from the normal strike target
(money generating) generators to avoid confusion. Later only control
points with factories will be able to spawn ground units, at which point
these will no longer generate income.
https://github.com/Khopa/dcs_liberation/issues/986
