system_design: additional constructor for java packets enabling in constructor initialization.
system_design: jaxb annotation for java packets enabling marshaling to and unmarshaling from xml.

Since Packets.Packet is an interface you have to annotate the holding variable with

@XmlElement(type=Object.class)
Packets.Packet myPacket;

Additional jaxb.index file has to be added to the classes, which will be generated by java_packets_jaxb_index containing all the packets.

Packets may also be marshaled standalone.
system_design: builtin types should not be included in jaxb.index
system_design: actions from meta communication should contain components, which they belong to enabling reverse search from component's and action's names to the action.
system_design: Primitive packages have to be listed in jaxb.index too.
Merge branch 'feature/system_design_java_xml_binding' into season2013