Unlimited power! (v0.4)

Well, finally done with one of the most important aspects of the game: powers! Armed now with a total of 6 powers, facing the enemy army becomes much more interesting. If only there were more than simple grunts to shoot at, though...

Changelist:

• Added Arrow Volley power (Keybind W). Shoots multiple arrows at once for better area coverage. Behaves exactly like the basic War Bow (Keybind Q);
• Added Fireball power (Keybind E). Shoots a single fireball that hits multiple clustered enemies (will cause a big explosion in the future). The aim moves up and down automatically, click to release;
• Added Lightning Strike power (Keybind A). Summons a lightning bolt from the sky upon the enemy. The aim moves left and right automatically, click to summon;
• Added Stonewall power (Keybind S). Summons a tall wall made of stone to block the enemy's path until they destroy it. Behaves like the Lightning Strike power, but the aim is on the ground.
• Added Boiling Oil power (Keybind D). Pours hot oil on the enemies knocking at your gates. Nasty. No need to aim, just click to drop it!
• Added cooldown indicators and UI icons for all powers;
• Many performance improvements behind the curtains. Probably impossible to notice in such a simple game, but my OCD certainly does!
• As always, the GDD has been updated accordingly.