Separated steady_states

Many of the ThermoSysPro models have a steady_state parameter to define whether to initialize the model:

• Either with der(state) = 0;
• or state = state0 ← user defined state.

Depending on the model, steady_state acts on P, Q, h ...

It would probably be interesting to separately initialize some of these variables. For example, I think that sometimes one may want to ease the initialization by providing the initial h, while still letting the model to evaluate a proper P and Q distribution (der(Q)=0 and der(P)=0).

I also have some examples where setting steady_state=false everywhere may lead to unbalanced system (P and Q @ estremities may be setted twice in adjacient components)