Using the new renderer stuff.

It is modeled after the vertex shader / fragment shader approach of modern OpenGL.
It also includes a texture extraction fragment shader, which hopefully will replace the current affine texture extraction.

This is still very much experimental, containing lots of todo's. For example it contains lots of if-hacks to select the correct fragment shader (for rendering or texture extraction).

Consistent 'REQUIRED' usage

Tabs to spaces in main CMakeLists file

Using 2 spaces for CMake code for now

Adjusted all includes, files and bindings.

In contrast to the MorphableModel member function draw_sample, this method takes blendshapes coefficients too and returns a full assembled mesh.

If 'REQUIRED' used inside 'find_package' there is no need to check '*_FOUND'
variable. And vice versa - if package is not optional then 'REQUIRED' can be
used instead of 'if(NOT *_FOUND) message(FATAL_ERROR)' block.

Apparently the dtype comparison compared pointer addresses, so it must've worked just by chance. Scary!

Also updated documentation

We copied this from the pybind11/eigen.h header. If we need it, we can always re-add it.

Let's see if there's ever a "modern CMake" solution for this without a custom target.
target_sources(eos INTERFACE ${HEADERS}) doesn't seem to be a proper solution.

Also swapped order of project() declaration and cmake_minimum_required()

30 is most likely a more reasonable default lambda for the new iterative shape-fitting - need to get some more experience with it

pybind11 deprecated .check().