Implemented Volume Control

Still getting used, to github and this was the first time that I used gitflow.
I hope I done this correctly if not please let me know.

I tried to stay with your code style and make my code look like yours.
If you have any thoughts on the volume implementation please let me know.

Best regards
Joshua Moody

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Implemented a basic Volume Control
- Added a property which wraps the player.Volume
- Added a method to change the volume level
- Added a submenu to change the volume level

Added a method to clamp an input value between min/max

Minor Refactoring:
- Wrapped the IsMuted/IsIdle inside a property
- Remove the else level since it was redundant and this reduced nesting.