Need to hide nav mesh in environments

[gfodor]

Moving the GLTF cliff environment to GLTF bundles (via #85) resulted in realizing a few A-Frame components are attached to the a-gltf-entity's involved and there is no way to represent them in the bundle format (nor likely should there be a way to do so.) These include the layer: reflection component on the cliff vista, the visible:false on the nav mesh, and the disabling of ar in the xr components. These will need to be rolled into the GLTF files and whitelisted as inflatable components.

https://github.com/mozilla/mr-social-client/blob/master/src/room.html#L240

[robertlong]

Blocked by https://github.com/MozillaReality/mr-social-graphicassets/issues/1