To Do: (new features or functions)
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Use OCAF format to represent Assy/Part model data.
  Save as an OCC.Core.TDocStd.TDocStd_Document document.
  Save any assembly in step format.
  Save Assy/Part model (TStd_Doc document) to file.
  Keep Assy/Part model in sync with Assy/Part view.

Modifiable parameters using treeWidgetItems:
  - Draw / Hide
  - Change Name
  - Change Owner
  - Change Color

Project face or edge onto active WP
Delete 2D
Delete 3D
View by current WP & Fit
RMB pop-up over graphics window:
  - Add indicator of current select mode


To Fix: (stuff that's there but not working)
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Get 2D Geom working (see: core_geometry_curves_2d_from_curve.py, OCC bottle)
snapping to intersection points on WP seems flaky
FitAll zooms out to infinity for WP's