Right now it just controls debugging options for what gets logged to the
console during execution. But at some point we should add on/off switches
for the two main facilities.
Also implements just enough additional commands to successfully render
the very first illustration in Joyce's Euclid, namely Book 1, Def I.2.
Since third-party code may not be loaded from the web in an extension,
requires bundling many GeoGebra app files into the extension.
Still to come: control panel for the extension.
So far, plugin only handles VRML. But it loads as a temporary plugin in
Firefox OK, and it generates viewers as necessary, including overlaying
existing images that are links to VRML files.
