Allow user to change background/wireframe color in 3D mode

From Aaron Bramson:

I am writing to again request the option for a white background for the 3D plots. For papers, posters, and presentations, the black background is bad (literally unacceptable for some journals) for screenshots. Real bad. This makes Netlogo3D useless for model visualizations for "real research", which is one of its (otherwise) strongest features. Adding a white background option should be super fast/easy to add as a check box in the 3D display settings dialogue.

This would include a change to glColor3f command in WorldRenderer->renderWorldWireframe, as well as the glClearColor in Renderer->init to be linked to either a __ command or an interface option. Because this is run in init, this code may not be satisfactory for changing the color on the fly.

Start by reading WorldRenderer->renderWorldWireframe and Renderer->init, then locate the 3D display settings dialog mentioned in the issue. Trace how the wireframe and background colors are initialized and determine how the selected option should affect them. Done means a user can choose a white background or alternate wireframe color for 3D plots.