Simplify dng names
Created originally on Bitbucket by daniel_fort (Daniel Fort)
Was already merged in Bitbucket before import, marked as merged by the import user
Remove "frame" from dng filenames so that it conforms with MLVFS default naming.
Issue: https://bitbucket.org/hudson/magic-lantern/issues/2609/update-mlv_dump
Discussion: http://magiclantern.fm/forum/index.php?topic=17992.new#new