Startup and initialization

RigelEngine's startup and initialization consists of the following steps:

1. Command-line options parsing (main.cpp)
2. Initialize SDL
3. Create window
4. Create OpenGL context
5. Initialize Dear ImGui
6. Load (or create) user profile
7. Create Renderer
8. Load NUKEM2.CMP and create ResourceLoader
9. Create DukeScriptRunner and load scripts
10. Load and resample all sound effects
11. Create initial game mode
12. Enter main loop