restore rendering demonstrations/tests

Updating these examples/tests to match the code restructuring that
went on over the past few weeks.
add color map

vtkgeojson writer now takes a flag that makes it produce no scalars,
  scalars mapped through lookuptable into rgb, or direct scalars.
geojson reader now recognizes which one it is reading
texture.js now has a lookupTable class which maps direct scalars
  on points through a table of colors
ogsvtk.py now demonstrates using this to draw by interpolating
  scalars across triangles instead of colors.

Conflicts:
	geoweb.py
Add color map capability to vgl proper.

The attribute storage mode detected by the geojsonreader now
propagates to the geometryFeature, which creates the
appropriate shader, with either a constant color, or interpolated
colors, or interpolated values mapped through a lookup table.
Merge remote-tracking branch 'origin/colormap_rebased' into next

* origin/colormap_rebased:
  Add color map capability to vgl proper.
  add color map
  restore rendering demonstrations/tests