MNT: Refactor more or less complete.  Caswell wants to continue refactoring, but the DEMO_plot1D.py and DEMO_plot2Dstack.py work now.
Merge pull request #13 from ericdill/refactor_2d

Refactor 2d
WIP : work on ControlContainer

 - can add nested containers
 - can add text and bare sliders
 - can retrieve both containers and widgets via qualified name

Still need to write code to create various control widgets.
ENH : added proto-type of enhanced slider class
ENH : added combo box widget

 - can add to ControlContainer
WIP : more prototyping work

 - proof-of-concept of class factory
 - proof-of-concept for building control boxs + plumbing