* Core:
- Remove the barely used system-info property.
- Use Gdk.EventKey for keyboard inputs.
- Make the init singal an error-throwing method.
- Implement disk handling directly.
* CoreView can be exposed as a joypad, a mouse or a pointer.
* retro-demo:
- Add pointer support from CoreView.
* Make all error domains internal.
* Make internal and port to C:
- GameInfo.
- Module.
- SystemAvInfo.
- SystemInfo.
- most of Core.
- keyboard keys.
