Added convert-dlna-scaled-helper.sh and updated convert-dlna-scaled.sh, ingest-profiles.txt

convert-dlna-scaled-helper.sh will invoke itemGen-scaled.sh using a list
 of DLNA-provided scaled reference content. Right now the list has 22
 profiles.

Updated itemGen-scaled.sh to take --skip-existing and --link-content
 options.

Fixed a bug in itemGen-scaled.sh dealing with files with multiple dots in
 the filename (H.264_720p_AC3_210s.ts was the culprit).

Added missing profiles to the ingest-profile.txt file.

TODO: Add scaled audio files to convert-dlna-scaled-helper.sh.