DupFinder Plugin: Distinguish between media master and file master

[sebastian]

The duplicate finder plugin handles only one media as master which is selected by the largest height among the duplicates. Ususally you upload smaller previews first and upload origianl files later. If the smaller and older media is already refered externally this small media will become invalid with the current implementation.

A better duplicate merging distinguishs between a media master and a file master. The media master could be selected by the view count and/or the older creation date. The file master could be selected by the largest files. With this algorithm the files of the older smaller media are replaced by larger files of the file master.

[sebastian]

Fixed in r512