The output is now *much* closer to the Vector shader output (mean
difference went from ~6 to 1.79), and in the multi-draw case it's
clearly visible that it's no longer slightly weirdly uneven.
The test files are now also much smaller as the originals were created
before RLE was implemented in TgaImageConverter.
Most of the testing scaffolding here is a preparation for the actually
complex formats like BC6/7 or ASTC. Also, it's great to be able to use
Magnum from Python to prepare data for testing the C++ Magnum APIs.
High-level docs with examples will be written once there's corresponding
support in MeshTools::compile() *and* in importer plugins, as skinned
meshes are usually brought in from files, never set up directly.
Co-authored-by: Squareys <squareys@googlemail.com>