Deleting obsolete and double defined Air.mo (replaced by package Air).  Not clear why I have to do this again, commited this before.
Different changes in the documentation, and ensuring that the new release control is used in the heat pump and boiler's heatsource models.
Revert "Deleting obsolete and double defined Air.mo (replaced by package Air).  Not clear why I have to do this again, commited this before."

This reverts commit a3f2f82d8a15df9c2441a6f15d543c918413fb8d.