Fix bug that kept submissions with rebased changes from showing up in the
"Discover" page in the 67724663687a version.


67724663687a:
I added preliminary support for rebasing changes from other wiki versions.

You can load a "secondary" archive to rebase from either by using
the "[rebase]" links in the "Discover" page or by explictly entering
an archive uri at the bottom of a page and checking the "rebase"
radio button.

The new macro:

<<<RebasedChanges>>> shows a directory level diff between the
parent version and the rebased version.

There have been a lot of changes and this release may be buggier
than previous releases.

If all else fails go back to the previous version:
USK@kRM~jJVREwnN2qnA8R0Vt8HmpfRzBZ0j4rHC2cQ-0hw,2xcoQVdQLyqfTpF2DpkdUIbHFCeL4W~2X1phUYymnhM,AQACAAE/jfniki_releases/0/

KNOWN LIMITATIONS:
o There is no file level diffing yet (probably for a while yet)
o You can't rebase into an empty archive.
o There is no support in the changelog or discover UI for rebased
  versions yet.
o Submitted versions are INCOMPATIBLE with all earlier versions and
  will cause spurious scary validation error. Sorry.