Display volume level support

[barcoboy]

Per the feature request on 2018-11-12 from schroedingersdog on the page https://forum.kodi.tv/showthread.php?tid=143912&page=24, I too would like to see the ability to display the KODi volume level on the LCD screen. It would be great to have a separate mode screen section in the LCD.xml file that would activate during volume level changes and stay on the screen a few seconds after the volume has been adjusted, but just a volume bar InfoLabel to display the volume level in other mode screens would be a good start.