[pvr] fix backend info never gets updated when only one pvr client enabled
[pvr] add ability to show free/used disk space of backend
[confluence] add pvr disk indicator in recordings view
Merge pull request #5303 from Glenn-1990/pvr_diskspace

[pvr] diskspace indicator in recordings view
Language and Settings: Rename normalizevolumes to maintainoriginalvolume
ActiveAE: Maintain original volume is the inverse of normalizelevels
Maintain original volume: Move it to expert settings and enable it by default