- spring cleaning the viewer:
 * removed controls' overlay from viewer (should be minimal, avoiding clutter)
 * changed handling of background color : now based on css background-color, as styling should be kept cleanly seperate
 * fixed styling issues, now correctly using @host etc
 * added screen capture utility js + handling inside viewer's code
 * various minor cleanups
- added new component : three-viewer-extra:
 * an enriched version of the base viewer, roughly equivalent to the base viewer's previous version
 * meant mostly as showcase of extending the base viewer
 * added ui elements for taking screenshots in three-controls and three-viewer-extra: some strange issues triggering "click" events on <a> elements to trigger download...
 * updated index.html : cleaned up, styling changes, experimentation
- some minor tweaks to three-editor , nothing to see