More scripting work

- added lookWithTouch.js - which is an example that implements our multi-touch look behavior in JS - closes #1828
- changed lookWithMouse.js to have alwaysLook mode - closes #1829
- change ScriptEngine to emit updates even when no octree servers - closes #1827
- first cut at spaceInvadersExample.js - closes #1830
- change invaders to use an absolute position based on game state - closes #1819 closes #1812