allow to use host database connection parameter

Add config option:
db_host (default empty) - name of host to connect to

winixd/core/config.cpp

@@ -181,6 +181,7 @@ void Config::AssignValues()
 
 	http_session_id_name	= Text(L"http_session_id_name", L"session_id");
 	db_conn_string			= Text(L"db_conn_string");
+	db_host					= Text(L"db_host");
 	db_hostaddr				= Text(L"db_hostaddr");
 	db_port					= Text(L"db_port");
 	db_database				= Text(L"db_database");