Add missing replaceable.

[qlambert-pro]

IDEAS.Templates.Examples.RadiatorHeating extends IDEAS.Templates.Examples.IdealRadiatorHeating and redeclares heating.
Unfortunately, in IDEAS.Templates.Examples.IdealRadiatorHeating, heating is redeclared without the replaceable keyword.

This PR adds the missing keyword.

[annadellisola]

IDEAS.Templates.Examples.RadiatorHeating extends IDEAS.Templates.Examples.IdealRadiatorHeating and redeclares heating. Unfortunately, in IDEAS.Templates.Examples.IdealRadiatorHeating, heating is redeclared without the replaceable keyword.

This PR adds the missing keyword.

The model IDEAS.Templates.Examples.IdealRadiatorHeating extends from IDEAS.Templates.Examples.BaseClasses.SimpleHeatingsystem where the heating model is already declared replaceable:

replaceable IDEAS.Templates.Heating.BaseClasses.HysteresisHeating heating
    constrainedby IDEAS.Templates.Interfaces.BaseClasses.HeatingSystem(
    final nZones=nZones,
    QNom={2000 for i in 1:nZones},
    Q_design=structure.Q_design);

Therefore the suggested change is not necessary.

[qlambert-pro]

Section 7.3.3 states:

Only classes and components declared as replaceable can be redeclared with a new type, which
must have an interface compatible with the constraining interface of the original declaration, and
to allow further redeclarations one must use redeclare replaceable.

And for whatever it is worth, we (Wolfram System Modeler) reject IDEAS.Templates.Examples.RadiatorHeating on that basis.

[annadellisola]

@qlambert-pro Thank you for addressing the issue.
Based on the Modelica guidelines, I have updated the model ‎IDEAS/Templates/Examples/IdealRadiatorHeating.