Allow to limit database listed
For now, we list all databases to which the server can connect and which looks like a Tryton database.
But on shared environment, we may want to use a single trytond instance but not list all the databases. Often the hostname is used to distinct the user prior to any authentication. So the hostname could be a parameter to list the databases.
I propose to add to ir.configuration an optional hostname. If it is filled, the database will only be listed for request matching the hostname.
I do not think we need to support many hostnames as this could be managed by using a redirect or setup a proxy which set the right HTTP_X_FORWARDED_HOST.