Delete verified dead code (~340 LOC)

Delete verified dead code (~340 LOC)

Classes unreferenced across engine, tests and all consumer repos
(demos, aukio, aukio-environment-fo4): geometry.Circle,
gui.ViewUpdateTimerTask, gui.humaninput.Connexion3D,
renderer.octree.raytracer.RayHit,
shapes.composite.solid.SolidPolygonMesh,
shapes.composite.wireframe.WireframeDrawing.

Also: ViewPanel.renderExecutor — a thread pool that was created,
resized and shut down but never submitted to; and the write-only
static renderFrameCount counter.