added diskspace information to service info (inspired by samans
approach, but differently implemented)
uh-oh fix
Merge remote-tracking branch 'origin/master'
changed: diskspace section in info service renamed to diskusage,
refactored to make use of the modern approach: vdr class cVideoDiskUsage
 offers access to numbers via methods UsedPercent(), FreeMB(),
FreeMinutes() and String()
minor cleanup