User list is now only retrieved using WebSockets

- removed users list ws message sent on connect (no point showing a contacts list when user has not signed in yet)
- do not send a users list on signout
- frontend: hide users list if any when not signed in
- fixed ws related tests
- drastically simplified view handling
- better decoupling between view instances and app data

r=@tOkeshu and others involved in related topics