Feature/#61 automatic open gl mock creation

Unfortunately, the generated mock is too large to be compiled. However, the mocks for all methods are there. If one is missing during implementation one probably has to copy the three entries per function manually from tests/src/mocks/generation/open_gl_mock.cpp/hpp into tests/src/mocks/open_gl_mock.cpp/hpp

If someone has an easier solution I am happy to try it.

Thorough revision is probably not needed since no new code is actually added to our source base.