checkpoint from vm for updates to contributor-edit update

This is primarily a checkpoint to capture COB status for work
done on VM, where my workflow isn't completely stable.

The ds-previous-values template factoring from the previous commit
was extended and moved to the dri2xhtml-alt theme, since the Mirage
theme inherits from it.

The edit-author interface updates were started in
Mirage/lib/xsl/core/forms.xsl, although JS updates have yet to be
started, and some input fields will have to be updated as well.

A few button-value strings were added to the messages.xml file
for il8n.