Closed caption changes and minor updates

## Closed Captions changes
 - New property ```showOffButton``` to show/hide the "Off" button
 - New property ```toggleActiveCaption``` - Will toggle the active caption on and off by clicking on it.

The default functionality of this plugin stayed the same. I only added new features behind configuration.

## Other changes
 - ```kMenu``` - Ignore ```<li>``` with ```.label``` css class
 - Disable buttons If their parent element has ```.disabled``` css class.

Please review and merge.