First pass at a new render widget

Still not complete, using GLEW for OpenGL extensions, and an X
implementation that uses more recent API to create OpenGL contexts
including OpenGL 3/4 if the required extension is present. This also
used XLibs directly for interaction, rather than going through Xt.

It needs a little more work to actually hook up something that will
render to the context, but it shows a great black window right now!

Change-Id: Ida0be9f2e9dc11ba3253ffd18cffa2e983ec954e
Implement a basic VBO based poly data mapper

This makes use of the code developed for the scene, but ports it to
a more direct use of VBOs in the derived poly data mapper.

Change-Id: Idb0db244abbb0e6857818589b20aae22e10abd53
Basic support for color from property

Change-Id: I3c62b6ce39afcb3f1abe59811f89e9064b23456d
Add the find module for Eigen 3

Change-Id: I1399f62495478622892247f8f1f9c6351c28cbba
Added a hack to override OpenGL overrides with GL2

This adds VTK_REPLACE_OPENGL_OVERRIDES (off by default) as a build
option, if enabled the vtkRenderingOpenGL module will be modified to
depend on vtkRenderingOpenGL2 (privately) and its overrides modified
so that we can replace existing implementations piece by piece while
running the full suite of regression tests (and seeing how close the
drop in replacement classes are).

Change-Id: I6decb741bde86270c43578e1b24dca4058de6781
some rough changes to the VBO polydata mapper
some more cleanup
added light override
compute cam matrix, add posiitonal light in progress
updates to support positional lights
Roughly mapping the colors/scalars, updates to shaders

Attempt to map the colors/scalars, and adjust the shader according
to whether color is a uniform or an attribute. Added some logic to
deal with building normals as the painters do, but error out for
now. This is also not even close to dealing with cell colors and/or
properties.

Change-Id: If584570b71dca4db3e9fd6c4ad95af58c00dea32
Normalize the colors, and put the light the other side...

This looks much better...

Change-Id: Ice9c05e6c10e13011164b120c3b3e23266cce414
change how object factory is done
Merge branch 'opengl2-rendering' of https://github.com/cryos/VTK into opengl2-rendering
some fixes to normals etc
added ambient color in
some module changes override actor change bunny color
changes in normal calcs
moved property over and started gutting it
Added the dragon model (already in external data store)

This should add it to the branch, the scene topic already pushed it
into the external data store.

Change-Id: Ic9888225c77459ebb0780eaa24d13b33896a9a65