Projectile trails, and other minor updates — Tower Knight Steam update #697032

Version 0.9.3 adds trails to arrows and cannonballs. This update also improves the knights animation when he gets hit by an enemy. Before, the sword just barely intersected with the knight's helmet, but with this latest update that has been fixed. Also, I've added 1 new challenge mode "Allied knight" which paves the way for more complex challenges that include friendly towers when maps are generated.