When clicking on a shopping tab like "contact", it changed the URL. But
changing the URL did not change the tab. Listening to URL changes
enables manual manipulation of the URL and simple links to "#/contact"
to open the contact tab.
Enterprise users have a new option to restrict their shopfronts to
logged in users only. If a guest visits one of these shopfornts, the
guest is prompted to login and is not shown any products.
Closes#849.
