Submission system - content edits

Edited messages.xml file and a few java files to incorporate content edits from https://docs.google.com/a/datadryad.org/document/d/1cyBCUBRihCKtVAqFNNMKgQS81qbrInoyJOIuM7gG-W0/edit. Verified on localhost.
This and 'Remove Voucher' also need to be updated in the file `dryad-repo/dspace/modules/xmlui/src/main/webapp/themes/Mirage/lib/js/dryad-pages.js`