Freecad.optics-design-workbench

* live display of rays during tracing (previously only updated displayed rays after an iteration was done)
* fix rays going to infinity being displayed with wrong direction
* add SimulationSettings.DistanceTolerance as a workaround for rays penetrating surfaces composed of many tiny faces
* hide a few not-yet-implemented features
* clean up worker process handling code, replaced global-variable/flag-file mix by synchronization entirely through flag files

* improved random number generator
* more verbose logging and logging to file
* renamed PointSource to OpticalPointSource for consistency

* implemented point light source with freely configurable angle dependence of emission power density
* implemented refractive, reflective and absorbing media
* implemented ray detector
* implemented storing ray hits and/or full ray trajectories to disk
* implemented process-parallel Monte-Carlo ray tracing simulation