Support turn_range for artillery type cannons

[TheKingJo]

I would love it and could make use of a turn_range support for artillery type turrets and ~ wagon turrets.

Currently they always have a 360° aiming circle regardless of the value that you set in the gun's attack_parameters of the artillery gun.

Now I dunno how the artillery logic is implemented, but a check for correct angle could be done quite easily
First checking for fitting range, then wheter a turn_range value != 1 is set, and then you would check for fitting angles via some normalised vector dot product and cosine calculations and a final comparison between turret angle and target position

[Silari]

Second.

[protocol_1903]

+1