Added start value for the newly introduced Boolean variables in
Modelica.Fluid.Vessels.BaseClasses.PartialLumpedVessel 
(they are used as start value of the iteration variables of the
mixed system of equations)

git-svn-id: https://svn.modelica.org/projects/Modelica/trunk@6890 7ce873d0-865f-4ce7-a662-4bb36ea78beb