Add "original filename: " in <note> if needed.

For some collections, the remediated metadata already contains
the "original filename: " string in the contents of the
<item_-_OriginalFileLoadedIntoOmeka_*> element. However, at least
one (George Plimpton) does not. So check and add it if needed.
Regenerate MODS due to check for 'original filename: ' string