Unit tests extended: check for unique permutations in allPerms; check Plot-level permutations.

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/vegan@2842 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
fix bug in plot-level permutations; now uses cbindAllPerms() for consistency. Bump to 0.8-3.

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/vegan@2843 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
reverse a small part of earlier fix which removed a reindex of the observations at the allPerms level

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/vegan@2844 edb9625f-4e0d-4859-8d74-9fd3b1da38cb