Remove manually-entered notes that contained the filenames

Remove (from the remediated metadata) the notes that contained the filenames of
the files loaded into Omeka - these note fields were manually populated within Omeka.
These notes are contained within <item_-_MODS_-_Notes_*> elements, so these elements
that contained filenames were removed.
This info is already included in the <item_-_OriginalFileLoadedIntoOmeka_*>
elements, which contain the filename generated by cul-omeka-xml within Omeka.
Change plmptn to PLMPTN in filename GeorgePlimpton.xml

It seems some of the filesnames were changed to lowercase before being
uploaded into Omeka - the original tiff stored by Digital Lab are all
of the form PLMPTN_004_002.tif. So changed all these lower-case
instances to upper-case instances.
Change .jpg to .tif in filenames in GeorgePlimpton.xml
Add item-in-context information