Redirect the user to his unique Domain even without Read right on the Root document

For now, the Domains are retrieve through a getChildren on the Root document, if a user has access to a Domain but not to the Root document, he is not redirected to the Domain but to his Home.

=> Use a query to find the Domains, and if there is only one, redirect the user to this Domain, otherwise fallback on what initServerAndFindStartupPage returned.