added brython v3 compatibility to glow module

I was seeing the updates and it seems glow module s not working fine. I made some adjustments to take into account brython v3 recent changes.

After that I get new errors that seems related only with `glowscript` and the `glow` module:

    Error: Property 'axis' must be a vec.
      module 'glow.primitive' line 16
        self._prim=prim(kwargs)
      module 'glow.primitive' line 16
        self._prim=prim(kwargs)

I couldn't continue with it as I'm not familiar with `glowscript` :-(

Please, review my changes carefully.