Use more descriptive resource group name.
MeshTools: don't return naked pointer from fullScreenTriangle().

Also make it possible to specify version for which we want it.
MeshTools: simplified fullScreenTriangle() code, fixed literals.
Minor cleanup.
Fully test query functionality.

The test now fails due to wrong result<bool>() implementation.
Fix return value from *Query::result<bool>().

This is just a convenience wrapper around result<UnsignedInt>(), so we
can implement it using that. And return true whenever the result is
nonzero (previously was returning true for 1 and false for 0, 2, 3,
etc., which is wrong). The tests now pass again.
Doc++
Fully test mesh functionality.

This was painful. The test currently fails for a few reasons, see
following commits.
Expose vertex attribute size as vector size + vector count.

Makes it possible to properly compute offset when adding matrix
attributes to mesh. The matrix-related test cases in Mesh test are now
passing. The vector count is now enum value to make it more clear that
that is compile-time constant independent of what was said in
constructor.
Fix index buffer offset in MeshView.

I'm not sure why I marked this as bug instead of fixing this directly.
The mesh test now fully passes.