Basic Engine

Implemented a basic service based engine currently containing:
- opengl_graphics_service
Currently:
Setting up OpenGL for rendering
Future:
Rendering different assets and a potential SceneTree
- event_service
Currently:
Accepting and distributing events to other services as needed
Future:
Buffering events, different handling of different events
-sfml_window_service
Currently:
Setting up the sfml window and giving sfml events to event_service
Future:
Support for more events like keyboard and mouse events
- cust_settings_service:
Currently:
Loads a very basic cfg-file and allows other services to access the
values
Future:
Implementing a more standardized cfg-file format
- input_service
Currently:
nothing
Future:
Handling the keyboard and mouse events as well as cameras etc.