New 3D Models

This update doesn't add much functionality. Instead, it now uses my own island mesh. It's created in blender and has roughly 4000 triangles - I hope this is ok even for some older computers. The other models (like trees and rocks) are from kenney.nl (nature pack and survival pack).

This is currently missing clearly identifiable landmarks. Those were the colorful pillars in the previous version, but in the end I will replace them with buildings or similar stuff. This is yet to be done, so in the meantime the game may be a bit more challenging than intended.