Adding a HTML description

Enhancement: Adding a opening with analytical calculation of the mass flow rate with respect to pressure (static and hydrostatique)

Error correction: wrong expression for mass fraction in the mass flow vector at ports

Modification to avoid issues when having a medium where the massFraction_pTphi function does not exist

Modification to taken account of buoyancy when gas with a lower density is at the bottom of the opening.

Correction: Mistake on sign of power. The power is positiv when exchanger cools the fluid A and heats up the fluid B

Correction: water inlet of the sensible part when the exchanger is considered as wet is TB_mid_2 and not TB_in

Correction of path to saturation function because old path derived from a partial package. This is no longer allowed

        substance notably):
                + atmosphere (source within fluidDynamics)
                + Opnening : compute X with 1 substance medium

        + combine vertical, simple and horizontal opening
        + ease specification of areaulic case and avoid mistake leading
        to unphysical air movment

        + remove initial equation (initial purpose was to help
                initialization by provided inverse function of homotopy
        + enable user to set T/deltaP ref used to compute damper Kv
        + fix homotopy simplified expr (to compute mass flow based on
            Kv)

	+ change x node var type ; to enable to be in block 2 .mat (for ModelicaScripting)
	+ use of add on for conductivity within wall (help for Persalys studies)