Enable a demo of the admin panel + update README

[shankari]

• add a new demo to display the admin panel
• update the README to:
  • change the download location to the base everest repo instead of US-JOET
  • clarify what the Joint Office is and that it will continue to contribute in this space
  • add section on launching the optional demo and displaying the admin panel
  • Modify the teardown to handle the case that there is no longer only one prefix