Extend automatic determination of turbulent region 

- SimpleGenericOrifice, PartialLumpedVessel: introduce parameter use_Re to determine turbulent region instead of using tiny system.eps_m_flow*m_flow_nominal
- TestPipesAndValves.SeriesPipes1 using SimpleGenericOrifice and zero flow works
- rename system.use_small to (not)system.use_eps_Re, which shall express that eps_m_flow covers flow reversal, while laminar flow is determined with Reynolds numbers
  (as opposed to m_flow_small covering flow reversal and laminar flow)



git-svn-id: https://svn.modelica.org/projects/Modelica/trunk@5920 7ce873d0-865f-4ce7-a662-4bb36ea78beb