[Smtk-developers] Large merge

[David Thompson]

Hi all,

I've merged a branch to SMTK that adds new functionality to the base Session class (a new way to transcribe) and additions to the discrete Session that take advantage of it. The discrete Session now properly transcribes use records as well as shell+loop uses. This is a significant change, so please let me know if you have problems.

Yumin, if you haven't pushed changes to master for the discrete grow and split operators, please be careful about updating since we have both made changes to the discrete Session. If you push your branch somewhere, I will be happy to get it working with the changes I've just merged.

Besides the changes to Session, this branch adds some methods that allow us to write Python-based image tests using the vtkModelMultiBlockSource. I hope to add some tests shortly that take advantage of this to provide better coverage of the CGM and discrete kernel operators.

	David