Add strafing logic

[Generalcamo]

The original RA had logic in which the yak would instead of dumping all of its ammo in one spot, it would dump it in a line. We should add this feature into openRA, with the following features:

If targeting a unit, the strafing unit will first dump ammo on the tile the unit is on, and continue on.
If targeting a building, the strafing unit will first dump ammo on the occupied tile that the strafing unit is closest to.

[zybiski]

yeah yak in ra95 would nuke groups of infantry with this. Now it's.. you'd sooner have them shoot the yak down and drop it on the infantry than relying on its machineguns to kill the infantry

[Generalcamo]

This is already hardcoded in TD. If this was made a YAML command instead of hardcode, then this could be closed.