Allow for precise positioning of object / camera

[msurguy]

It would be useful to allow precise positioning of object / camera for fine grained controls

[osresearch]

Not a bad idea. I've done it "manually" for repeatable testing of some error conditions by opening the javascript console and updating the eye_theta, eye_psi values and then forcing a re-projection.

p5js has input boxes, so we can probably use one of those in the GUI, although my first attempt interfered with the keyPressed() function, so I'm not certain what the best way to do it is.