Merged some turret classes

core/src/mindustry/entities/bullet/ArtilleryBulletType.java

@@ -14,6 +14,7 @@ public class ArtilleryBulletType extends BasicBulletType{
         collidesTiles = false;
         collides = false;
         collidesAir = false;
+        scaleVelocity = true;
         hitShake = 1f;
         hitSound = Sounds.explosion;
     }

core/src/mindustry/entities/bullet/BulletType.java

@@ -61,6 +61,8 @@ public abstract class BulletType extends Content{
     public boolean collides = true;
     /** Whether velocity is inherited from the shooter. */
     public boolean keepVelocity = true;
+    /** Whether to scale velocity to disappear at the target position. Used for artillery. */
+    public boolean scaleVelocity;
 
     //additional effects