MeshTools: renamed clean() to removeDuplicates().
MeshTools: this can be moved instead of copying.
MeshTools: added duplicate() utility for creating non-indexed array.
No need to add `#line` directive also before `#version` line.
Properly number shader sources.

Previously the sources were numbered 1, 3, 5 etc., which is wrong.
Shaders: ported MeshVisualizer to not require geometry shader.

Wireframe width and smoothness isn't ported yet, because I don't fully
understand the behavior of standard derivatives in fragment shader.