Build 0.5

This patch comes with a few more balance improvements aswell as some new mechanics.

Gameplay:

- Enemys come now in waves from different directions 

- Added bow upgrades depending on the amount of enemys you kill

- Added a final Boss 

- Player has now a healthbar 

- Added a few more sounds

- other minor bugfixes

UI:

- Improvments to the main screen

- Added a volume slider at the mainscreen which safes your settings from the last session

- Scorecounter added to the bottom right of the screen

- Added a final scene that shows if you kill the boss slime

- fixed some bugs with the UI that occured when playing in different resolutions