Updated the Getting Started for the new version of CellBlender

Took the first page from zero to visualization. Some of this
had been on subsequent pages when MDL editing was required,
but with CellBlender it seemed like it might work on one page.
Initial version of the CellOrganelle12 tutorial

Pulled the text out of mcelltutorialtranscript.pdf (from Ben) and
watched the movie beng276_MCell_demo_3a.mov (also from Ben) to get
started. Spent a lot of time creating a GIF file to describe the
model that's being built (cellmodel.gif and cellmodel_s.gif).

I was able to run the demo all the way through, but the tutorial
is still just getting started.

This tutorial was started using:
  CellBlender Source ID = 51e3abf95f840f76e3af04c5bf4c2d5114122ebf
Merge https://github.com/cnlbob/cellblender_tutorials

Conflicts:
	getting_started.rst
	images/gs_define_reactions.png
	images/gs_model_init.png
	images/gs_model_objects.png
	images/gs_new_molecules.png
	images/gs_new_region.png
	images/gs_surf1_rel.png
	images/gs_top.png
	images/gs_vol1_rel.png