Add further graphics options in Graphics Editor

[rchristie]

Several Graphics settings, many quite obscure, are not yet editable in the GraphicsEditorWidget, including:

• Graphics name (probably needs Scenefilter to be exploited first)
• Streamline seed element (streamlines need some testing and fixes in Zinc first; stops on some element boundaries).
• PolygonRenderMode can be an enum chooser instead of a wireframe flag (but it won't make a difference until more modes are added).
• Font chooser needs to be tested once there is more than one font.