Grouping of balises and their attributes

As mentioned by Pierre Simon in the forum entry [http://www.railml.org/forum/ro/index.php?group=1&offset=20&thread=53&id=147] it is useful to repeat the single balise's attributes within a group of balises. The following solution is suggested:

• A baliseGroup is modelled as an element with ID and name and therefore inherits the parameters id, name and code.

• A baliseGroup fulfills a certain function, which will be defined in the parameter type with the possible values infill, signal, technicalFixed and technicalSwitchable.

• A baliseGroup may have a reference to a signal, which will be defined in the optional parameter signalRef.

• The reference from a baliseGroup to up to eight single balise elements remains with the sequence of baliseRef objects.