Hide the 'Next' button until a license is chosen.

When uploading an image the 'Continue' button only appears after the
files have uploaded, it therefore makes sense to show the 'next' button in
the license step only after any deed is selected.

This removes the need for the NullDeed

Change-Id: Id9551311d833ace26abff4bec1ad136a84206168
Merge "Hide the 'Next' button until a license is chosen."