update & port to Three r68 (current master)

[antont]

tested to work withour errors with local gltf and xml3d / suzanne examples and client-server with the Physics2 example.

also ported Pong similarily, wasn't much and seems like kind of nice (albeit contraversary) change that unassignability .. modifying the existing vector objs seems sane: https://github.com/playsign/PongThreeJS/commit/0ede0815b8db9abdf72c9e48af1a906bf89fcc5d

NOTES / not done yet:

• breaks Ludo's avatar / skeleton examples as the skel things have changed in three.js
• i didn't check for updates in the threeX plugins we use