Unit composition is defined by the doctrine. The most understaffed CP
will now get the most underrepresented unit type. Previously a random
understaffed CP would get a random unit type.
Fixes https://github.com/dcs-liberation/dcs_liberation/issues/1057.
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.
