New functionality for the real estate agencies to create and add agent accounts to their profile

The real estate agencies (main user account) now have the possibility to create and add additional real estate agent accounts with their own username, password and profile information. Every such real estate agent is able to log in with his own username and to list and manage his own properties - the list of agents for every agency shows up on the main site, when opening the agency details page. Also for every real estate agent / sub account, the main user can set to which other pages in the agent admin panel he should have access to (in this way it's possible to give different permissions for the different agents and allow or deny them access to selected pages).