[pvr] fix creation of an illegal group path in GetGroupList()
[pvr] fix creation of item paths for root (pvr://) directory
[pvr] fix: remove slash at the end of the base path
[pvr] removes Timer and Guide item from root directory listing
Merge pull request #5831 from xhaggi/pvr-fix-getgrouplist

[pvr] fix pvr:// directory fetching