Clean up shaders

[slimsag]

We declare shaders in the examples as []byte in the Go source code -- which is semi confusing for people reading over it (mixing between Go->GLSL->Go etc). We should instead declare these in seperate .vert and .frag files in the example's directory (and comment them well).

See azul3d-legacy/gfx-gl2#1

[Seb-C]

Do you plan to use a tool to include the .glsl files in the compiled binary, or is it fine to just load an external file (from Assets ?) ?

[slimsag]

@Seb-C loading an external file is fine.

The asset folder has been done away with, so each GLSL shader source would just go into the program's source directory (e.g. azul3d_texcoords folder). You can see this in the gfxv2 development branch.

[slimsag]

This was addressed by #6, so closing.