Pintle mounts handled incorrectly

[assaultdoor]

Environment: stand-alone MegaMekLab 0.49.15, MacOS, OpenJDK Runtime Environment (build 11.0.19+7)

There is no easy way to have pintle mounts on the front or rear of a vehicle. There are checkboxes in the Structure tab for left and right mounts only. I can remove those and move them around in the Assign Criticals tab, and units with front or rear pintles are validated, but this is awkward.

The description of pintle mounts on TM p. 234 says they provide a 180-degree arc "along the side of the vehicle", which suggests they should be left/right only. However, TM p. 137 and TO p. 255 both specify left, right, front, or rear. According to Xotl, "side" includes front and rear.

Also, vehicles such as the Apocalypse World Rover and the Pintel Heavy Combat ATV have pintle mounts with a fixed mass and no fixed weapons. According to Xotl, this is allowable. However, it does not seem to work in MegaMekLab. (Note that in this ruling, Xotl again says that pintle mounts can face forward.)