Tower Defense V0.9 - Upgrades

Game Addon: 

-Enemies should no longer get clumped into long lines
-Enemies will now scale much more with levels

New element: Upgrades
-All towers will be allowed 4 upgrades, and they will cost 4/8/12/16 gold to apply.
-Upgrades can be stacked, for 100% of the value each time.

New talent: Upgrade Damage
-Increases tower's damage by 25%
-This is lowered to 15% for Chain Lightning Towers
-Increases Player Heal Tower's mana, stamina, psi, and health gain instead
-Has no effect on Wall Towers

New talent: Upgrade Health
-Increases tower's health by 50
-Wall Towers instead gain 2.5 life regeneration
-No effect on Player Heal Towers

Fire Tower
-Range reduced to 3
-Cost reduced to 6

Chain Lightning Tower
-Cost increased to 18
-Can now fire through allies