Big troubles with loading textures to OpenGL

This problem will be solved with the introduction of dynamic runtime shader loading in the program, but just as a note I will post the problem here.

Loading textures into GLSL requires 2 things

1. something like this: `ShaderUtilities::setInt(model_shader, "depth_map", 4);`
2. then something like this: `glBindTexture(GL_TEXTURE_CUBE_MAP, depth_cube_map);`

Notice how we must store the information somehow.

The issue names ShaderUtilities::setInt and glBindTexture but no files or tests. Start by locating those entry points and tracing how shader and texture information is currently stored. Clarify the dynamic runtime shader-loading design and define a reproducible check for loading textures without losing that information.

Written by the indexing model from the issue text.