DMPlex: fix VTU viewer when field/components have not been defined

The parent commit added support for writing field/component names, but was
broken when only the number of dofs is stated.  Now when the user does not
specify field names, use

  {VecName}{Cell_or_Point}Field0.{i} for i in 0:bs
DMPlex: fix VTU writing cell fields without similar vertex field
Merge branch 'jed/plexvtu-cell-without-vertex' into next

* jed/plexvtu-cell-without-vertex:
  DMPlex: fix VTU writing cell fields without similar vertex field
Merge branch 'jed/plexvtu-fields' into next

* jed/plexvtu-fields:
  DMPlex: fix VTU viewer when field/components have not been defined
DMPlex: Added DMPlexRestoreCone/Support() to F90 interface definition header
- Also added to test ex1f90
Merge branch 'knepley/plex' into next

* knepley/plex:
  DMPlex: Added DMPlexRestoreCone/Support() to F90 interface definition header - Also added to test ex1f90
DMComposite: fix use of column count after MatRestoreRow
Merge branch 'jed/mat-restore-zeros' into next

* jed/mat-restore-zeros:
  DMComposite: fix use of column count after MatRestoreRow