E.g. '--playlist-items 2-4,3-4,3' should result in '[2,3,4]', not '[2,3,4,3,4,3]'
Not using cache results in redundant network I/O due to downloading the same pages while using --playlist-items n-m
Fix for JSON meta data download(closes #13651)
Added fixes according to #13651 and user @remitamine