Graphic improvements

[dominik-zeglen]

This MR adds a few graphics improvements to the game:

1. Fixed tonemapping, gradient banding and added dithering
2. RGBA16F output is used through the whole graphics pipeline correctly
3. Skyboxes are loaded as sRGB images properly now
4. UI meshes, like hp bars and name tags, are now culled from displaying
5. Gaussian blur is replaced with dual filter kawase blur for the bloom effect
6. Moved UI rendering to separate render pass on top of existing canvas, vastly improving performance