Add Shader System

Initial Architecture for OpenGL Shader with 2 Basic-Shaders(where will be support for
dynamic Directory-Paths in the Future)
The Shader System exists since the first created Game Window and terminates if the last
Game Window is closed.
The Engine can handle only 1 Graphical Backend(and Shader System), until there will be
an option to change the Graphics-Backend at Runtime if there will be other APIs than
OpenGL implemented.