DMPlexVTKWriteAll_VTU: fix writing vertex data
DMPlexDistribute: fix label distribution

This old code was not advancing to the next label when it finds "depth"
(which is not distributed), thus it just compared "depth" multiple times
and never checked the other label names.
Merged in jed/fix-plex (pull request #9)

DMPlex: label distribution and vertex viewing
bib: publisher names should not include "Inc.", according to Gail