Refactor renderers

[SamVerschueren]

The entire render stuff should be refactored to easier allow multiple different and even custom outputs.

[andywer]

Would love to see that. We still need a fix for #11 / #12.

Was already trying to fix it on my own, but then recognized that it would require refactoring the rendering process a lot.

[SamVerschueren]

This is really close to being resolved. Only need to write documentation.