expose default* to config

[nonchip]

setting the defaultRendererName et al requires to edit the js sources, should be exposed to config.

[leonklingele-work]

Why would you want to use a different renderer name?

[nonchip]

because i want to use a different default renderer, obviously. defaultRendererName sets the view (stuff like "large view"/"kiosk"/"auditorium") that's opened when joining a room. and different use cases require different views, so i feel this should be configurable instead of having to edit the source code.

in my case that's the "large view" because there's no reason to see yourself as giant as the people you talk to if you want to talk to people instead of using your webcam as a mirror, in other cases it might be the auditorium view if it's e.g. an online lecture service