- This is the first change toward making it easy to add new polygon modeling features in external plugins (or through scripting!)
- Added a new 'PolygonModeling' module to the MeshEditor plugin and moved the TessellatePolygon feature there
- New UMeshEditorPolygonCommand ABC class (and friends) for polygon editing features to inherit from
- MeshEditor now has a very minimal public API
- Experimenting with using multiple protected 'contract interfaces' for FMeshEditorMode to reduce public API size
- Some initial clean-ups to how selection/deselection works (reduce boilerplate.)
- Removed a bad use of 'friend' for FMeshElementViewportTransformable
- Moved a few functions around to either make them publicly accessible or to hide them
- Slate: Added support for registering UICommandInfos without a 'this' pointer
#codereview richard.talbotwatkin
#rb none
[CL 3367605 by Mike Fricker in Dev-Geometry branch]
