Fix vtk buttons warnings (closes #38)
Merge branch 'Issue#38'

* Issue#38:
  Fix vtk buttons warnings (closes #38)
Fix buttons startup state (closes #36)
Merge branch 'Issue#36'

* Issue#36:
  Fix buttons startup state (closes #36)
Fix sturtup state. link show button show label state.(issue #36)
Merge branch 'Issue#36'

* Issue#36:
  Fix sturtup state. link show button show label state.(issue #36)
Add point and contour visualisation (Issue #20)

Also improve Help|About text, finding of time-varying mapper for
time player widget.
Tidy up Grid Viewer example data (Issue #20)
Add Grid Viewer testing. (Issue #20)