Add non-existing users

In many places, we would like to be able to refer to TU Delft staff and students who have never signed in to ProjectForum. Logic should be put in place to automatically create the user accounts for these users based on the LDAP to properly link the roles. Something like this may also need to be implemented for inviting users to companies (make user, mark as "autocreated", if marked as "autocreated", ask for additional details upon first sign-in.)