changes to parallel tabs sections implementation:

- nParCir is now set using a parameter instead of using a record
- added some more divisions by nParCir
also cleaned up code a bit
this is not correct. For a network with n identical parallel circuit, the overal pressure drop equals the pressure drop of one leg through which m_flow/nParCir flows. Here dp_nominal is calculated correctly but not the mass flow rate which is used for the pressure drop calculation within the twoPort.

We need to discuss the best way of implementing it.