Adds QoL feature for Mortars:
'Call Best Shooters' button on mortars to auto-assign best shooters map-wide.
Select all mortars and press the button and the same number of pawns will be drafted and move to the nearest selected mortar to operate it.
- Uses mortar accuracy stat to choose best pawns for the job.
- Only works if you select the number of mortars first before pressing the button.
