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.
Comments and fixes
Added API to set / get scalar format
Removed shader that hard-coded the color
brought back solid color shader and cleaned up detection of scalar type

Now color type choice is based on the presence of the scalar field, or color field, and lookup table range is automatic.
Brought back the solid color shaders, as we need a way to specify the one color in the case when the data itself lacks colors (e.g. country lines).
Added this as a new material type, so that it doesn't preclude the use of the old material which assumes color is present. More cleanup needs to be done here, the solid color should be specified on the "actor" level, like opacity is done now.
Merge remote-tracking branch 'origin/colormap_rebased'

* origin/colormap_rebased:
  brought back solid color shader and cleaned up detection of scalar type
  Removed shader that hard-coded the color
  Added API to set / get scalar format
  Comments and fixes
  Add color map capability to vgl proper.
  add color map
  restore rendering demonstrations/tests