GUI fixes: Add escape drawing, disable right-click drag, disable double left-click

[mrariden]

• Add escape drawing by hitting escape key.

• Disable unused right-click and drag to zoom behavior. This is not needed because other zoom controls exist and right-click to drag occasionally gets in the way of annotation.

• Disable double left-click to reset the view. This was especially painful when looking at orthoviews in the 3D gui and quickly clicking around to see the orthoviews update.

• Update docs to describe escape draw behavior

• GUI testing protocol

• tests passing

[mrariden]

This would be a good opportunity to de-duplicate the keyPressEvent code that is present in both gui.py and gui3d.py. I would pass the events that can be handled by the parent class up the hierarchy, so the 3D key press code is specific to the 3D GUI.