Added setListener to CheckBox, Menu music now toggleable

- Overloaded CMusic::PauseMusic to resume paused music when called with
'true'
- added some missing Listener updates to MenuSlider
- Checkbox can now store a Listener that gets notified on Checkbox
toggle
- added Checkbox to options menu to pause/unpause menu music
- fixed a spelling error and closed a bracket in todo list (honor pls)