Fixed utility slot issue on higher tier purge trooper units.

Purge heavies will only spawn as leaders in FL 1, adjusted their spawn rate and hopefully should be the last update in regards to spawn rates.

Adjusted Spawn weights on units Heavies should (theoretically) spawn less frequently in early game. Also the Purge heavies become followers at FL2, they still appear at FL1 as a leader unit.

So I borked the Spawn weights on these units and this update was to tweak them to be more reasonable. Also made the Tier 1 Purge Heavy a bit slower so you can run away from them better.

Took one armor off the Purge Heavy since one player was unable to beat them at FL1.

Adjusted the aim of the Purge Heavys to be less high. Also added more compatibility to other alien mods.