WireJunction: Added @wireJunction property for the Sequence Chart tool.

This allows to recognize the top level wire junction modules and open their
axes when the network node level filter is selected. Otherwise these modules
are not open (because they are not full network nodes) and this prevents packet
transmissions to be seen.

src/inet/physicallayer/wired/common/WireJunction.ned

@@ -24,6 +24,7 @@ package inet.physicallayer.wired.common;
 simple WireJunction
 {
     parameters:
+        @wireJunction;
         @display("i=misc/node_vs");
         @signal[packetReceived](type=cPacket);
         @statistic[packetReceived](title="packets"; source=packetReceived; record=count,"sum(packetBytes)","vector(packetBytes)"; interpolationmode=none);