Update modelica documentation for bestest_hydronic and bestest_hydronic_heatpump

[EttoreZ]

This issue is a follow up to #555. In particular it was too cumbersome to update Modelica documentation for testcases bestest_hydronic and bestest_hydronic_heatpump, since it would require updating the IDEAS library, and they use an older version. Therefore, once the case studies are updated to Modelica 4.0, the documentation will also be updated to add the activation inputs.