Side Bar: Usability Issues

[jdittrich]

There seem to be some usability issues with the sidebar which displays the user names.

1. Icon:
   * The sidebar is a list and not a menu. Thus I think the hamburger is not ideal (or is this already standard for lists as well?)
   * As an alternative we could use "other users", "members" or the like. together with an toggling arrow/triangle
2. Opening and closing:
   * The Hamburger Icon seems to have a toggle interaction. The bar covers the icon itself when open, thus closing the bar itself is not possible.