#3 Methods for resizing the window

[snarxfgl]

The framework needs methods for

- Resizing the window or changing the fullscreen resolution
- Enabling or disabling fullscreen mode
- Toggling fullscreen mode

Currently, the resolution can only be set at initialization using the framework parameters. Then the user can resize the window or toggle fullscreen by pressing ALT+ENTER.

Optional functionality:

- Allow/disallow the user to resize the window
- Allow/disallow the user to toggle fullscreen with ALT+ENTER