Have superadmin and guest settings configurable

FTR my original rationale for superadmin user having the text editor by default was:

  • Superadmin is a technical user. The most technical one actually. Thus it makes sense to provide the technical editor for it.
  • The wiki editor allows to do everything and without risking mistakes. When using the WYSIWYG ones, it’s easy to make mistakes and break things when you edit technical content (extra new lines, conversions, etc). The text editor is not easier to use for making tech changes but it’s also safer.
  • The superadmin user is off by default and is a user that’s not supposed to be used except when you broke your permissions in your system and you need to change them back. It’s definitely not a user that you should use to edit pure content. It should only be there to edit technical content and the text editor is the best editor for technical content.