GUAC-637: Add zoom controls to menu. Move clipboard to top.
GUAC-637: Update contents of zoom state when scale is changed.
GUAC-637: Use setScale() only to set display scale. Update auto-fit checkbox from within setScale().
GUAC-637: Implement auto-fit checkbox.
GUAC-637: Implement zoom in/out. Fix auto-fit checkbox logic.
GUAC-637: Fix auto-fit disable logic.