Renaming and integration of new buoyancy heat transfer models
requested to merge github/fork/DaJansenGit/issue309_fastHvac_changes into issue337_heatTransferStorage
- renamed models according to the AixLib Namespaces
- integrated three new buoyancy heat transfer models which were developed by Christian Grozescu
Still to do: Change variable and parameter names according to the AixLib Namespaces @SebastianStinner could you merge it?