Update v1.61

Update v1.61 (5/2/2019)   "Bug fixes and difficulty balancing"

-All singleplayer difficulties now allow 4 soldiers per unit
-Increased infected base stats 
-Reduced infected stat multiplier based on difficulty
-Increased infected detection radius
-Increased shotgun and pistol damage
-Increased player movement speed
-Removed player starting movement momentum
-Improved flashlight
-Fixed aiming bug
-Fixed bug where infected would stop at open doors