Move excel field table row to a partial
Fix excel date field uploading

This was actually never working. Javascript wasn't setting the flag to
convert an xls date field and the date was just getting sent through in
the magic floating point format the excel file stored it in.
Redo the form for mapping excel fields
Change handling of excel case field input

Now the list default populates with the values from excel fields
Merge branch 'case-importer' into staging2