Exclude additional files from source control.

Note: resource.py will be autogenerated.
Package existing work from Harmony.

Change Harmony references to Riffle.
Use new icons.
Define icon factory for returning appropriate icons in standard manner.
Simplify documentation structure and add initial text.
Remove unused imports.
Clean up setup file and add missing dependencies.
Fix dependency versions.
Build resources as part of setup.
Use global for readme path.
Support passing iconFactory via browser to model.
Add basic usage documentation.