Make it easier to re-download a zip.
Make it easier to re-download a zip.

Change the revision part of the export message to be a direct link
to the zip file. This provides the user with more options to
download the zip if they want, or if for some reason the hidden
iframe download doesn't work.

Change-Id: I854d71d95c89a37e5c5618753309581a2b07f8fc

jmorse/cyanide,jmorse/cyanide,jmorse/cyanide,jmorse/cyanide