Restructure page locations and form flow

This implements Anne-Sophie's revised site designs from: https://bugs.caret.cam.ac.uk/browse/PAVO-175

The previous contents of /me are show shown on the home (/) page when logged in. When logged out the home page shows the previous info content.

The form is now @ /upload. The file is uploaded as a content item before the main form is presented.
It's outside the returning function because it's a constant which is independent of any single widget instance, so doesn't need to be created in each widget.