idealSource does not simplify when allowFlowReversal = false

[Mathadon]

We currently have

  port_a.h_outflow = inStream(port_b.h_outflow);
  port_b.h_outflow = inStream(port_a.h_outflow);

which should probably become

  port_a.h_outflow = if allowFlowReversal then inStream(port_b.hi_outflow) else Medium.X_default[1:Medium.nXi];
  port_b.h_outflow = inStream(port_a.h_outflow);