While namespaces act for hierarchy, modules are something like "tags" -
usable when you want to check related classes of e.g. CubeMapTexture.
Not sure how to name module for Math and Physics namespaces and
Contexts/Trade, though.
All classes moved to MeshTools::Implementation namespace and removed
from Doxygen output. They now all return tuples instead of custom
structures. Updated and improved documentation, removed references to
implementation classes.