Make test for "original filename:" case-insensitive

Make test for "original filename:" case-insensitive when looking
at contents of <item_-_MODS_-_Notes*>. Reminder: we want to
ignore the <item_-_MODS_-_Notes*> that contain filenames of the
files loaded into Omeka, since that info can, and should, be
retrieved from the <item_-_OriginalFileLoadedIntoOmeka> instead.
element.
Regenerate MODS due to "original filename:" test change.

The test for "original filename: " in the content of
<item_-_MODS_-_Notes*> was made case-insensitive.