SqlServer: support single sign on / Windows credential authentication This is done through a new db-extra-arguments section in instance_dir/sources which is passed as a string to the extra_args named argument of lgc.db.get_connection. If this argument is Trusted_Connection, windows authentication is used instead of login/password. This change requires at least revision 5475ec3f6412 of logilab.common which will be included in logilab-common 0.46. debian/control updated to mention this new dependency.