Completely re-wrote the mod.

The ML 3-inch Mortar now has its own custom stats. White Phosphorous and Counter Barrage available.
Every mobile artillery gun and mortar can be garrisoned in the pit to get +15% range on all barrage abilities.
Once constructed, the pit becomes neutral, so it can be garrisoned by anyone.

Mortar pit now gives trench cover instead of garrison cover.
Decreased maximum time to garrison from 5 seconds to 1 second.
Increased armor from 5 to 30.
Fixed Ostheer GrW 34 and mortar halftrack ignoring trench cover.

Fixed empty mortar pit speaking and mortar crew being silent.

Initial release.