v1.1 Rework

Reworking this project to make it a little more appealing and (hopefully) fun :)

Thing that were changed:

•  Redid waves 1-10 to reduce the amount of randomness, making sure the beginning of the game does not become unplayable
• Reworked the random wave algorithm after wave 10
• Added boss fights every tenth wave, with three different boss types: one bounces, one shoots and one moves menacingly!
•  Now recovers one health for every 50 enemies killed
•  Changed Upgrade order to guarantee Shot Cooldown upgrade on wave 3
• Behind the scenes: Untangling my old code, making it more readable and removing a lot of redundancies
• Adding this changelog! :)