Clearing buffers in a sugested way

Clearing buffers in a sugested way:
https://www.opengl.org/wiki/Common_Mistakes
Corrected transparency issues on FileNodes

Corrected transparency issues on FileNodes - now they are perfectly
transparent with no artefacts. The key is to use
GL.DepthFunc(DepthFunction.Always) instead of GL.Disable
(EnableCap.DepthTest). That's because disabling depth testing makes GL
also disable writes to depth buffer.