Move designer url elements to Guvnor's configuration

Designer URL example is 'http://localhost:8080/designer/'
Since Designer must run in the same domain where Guvnor is running, 'protocol', 'host' and 'port' elements can be dynamically obtained in Guvnor.
These values must be stored as part of Guvnor's configuration so they can be used in Guvnor later.
The application context name ('designer'), will be defined in Guvnor's preferences.properties file.