Clean up filenames

This included removing the url part of the name, just keeping the actual
filename. This also included changin .jpg to .tif
Only did the above for filenames in item_-_OriginalFileLoadedIntoOmeka_.
Did not touch the filenames entered manually and included in
<item_-_MODS_-_Notes_1>Original filename: ..., since we won't
be using these.