Rework How Tuple Lists Are Handled

[jmwright]

Currently, any controls that require a list of points (tuples) have their own point controls and it gets a little messy. My proposal is as follows, and I think that this should be a prerequisite to #47

• Add tuple list support to the parameters dialog.
  • The cleanest way to do this might be to create a table-like control where users can enter the numbers.
• Change the point list controls inside the spline, polyline, etc controls to be an option button.
  • Add a New option to this button that launches the parameter dialog if the user selects it.
  • Allow the user to enter the points list and then set that new list's parameter name as the selected option.
• Clean up things like the text field width to make the parameters box look nicer.

One of the main points of Semblage is to permit parametric design, so this seems like a natural fit.

[jmwright]

• [x] Add tuple list control to Add Parameter dialog.
• [x] Implement tuple list save.
• [x] Implement tuple list load.
• [x] Add drag and drop capability for list items.
• [x] Add right click menu for Add and Remove.
• [x] Integrate new tuple lists into controls that use them.
• [x] Add tests for new functionality.

[jmwright]

Completed in commit b26ea39859e3e5efee7717e1e832eaaa73de61f8