Workplane Visualization is Not Always Visible When it Should Be

[jmwright]

• The visualization will disappear after adding a parameter when that should have no bearing on whether or not the workplane visualization is visible.
• Adding a workplane to an object will make the original object disappear and there is no workplane visualization to replace it.

The untessellated check in the ContextHandler class should probably check to see if there is a Workplane().tag(), workplane().tag() or just workplane() call at the end of the code. If there is, a workplane visualization should be created. It would also be interesting to explore the possibility of removing the selector and workplane from the end of the chain, then render what was there before, and then add the workplane visualization on top of that. That would save a lot of confusion with objects and workplanes disappearing after operations are added.

[jmwright]

I'm not completely happy with the implementation, but I think it will work for now. Semblage will eventually need a much more sophisticated way of understanding the script-render context, but I'm hoping that the work on selector synthesis will help provide some ideas on that front.

Ref: 0596c20e9b354aca7dc57d88d6619337f376b67e