Add multithreading and a lot of renaming

1. Implement multithreading when loading meshes, resulting in major speedup.
2. Add Thread_pool class.
3. Rename class and function names (MISTRA C++).
4. Rename meshes.
5. Update readme.

Signed-off-by: Samuel I. Gunadi <samuel.i.gunadi@gmail.com>
Merge branch 'master' of github.com:samuelgunadi/openglproject