GitLab

* added a page with general information for usage of external router and some more specific information for some vendors
* added page with some general router debugging information and with LED codes from the StuStaNet Router
* added links on main support and selftest page to the pages

See merge request stustanet/stustanet-website!18

* added note about router webinterface for reconfiguration
* further encouraged sending more information in the mail
* fixed a broken link
* added note about free time work
* removed image captions and replaced one image
* added note about data saver extensions