- "picking" now works both in perspective and orthographic projection modes
 * some additional adjustments and clean ups to selection-helper and main viewer
- added camera positioning control to main vieweer /three-controls/three-viewer extra
 * allows setting view orientation: left/right/front/back etc
 * some additionnal tweaks to controls speed as well (slightly faster/more reactive)
- added demo for loading & displaying models (stl loader from three.js)
 * added demo files from three.js
 * added stl-loader.js

- added keyboard handling for three-viewer and descendents:
 * added auto focus on "click" so the keyboard event bindings behave normally
 * added experimental support for model deletion (just press the "del" key to remove an item)

- various minor improvements and experiments in viewer and viewer-extra: