SYSPHS12 — Suggest SysPhSLibrary should support Heat and FlowingHeat as conserved quantities with HeatFlowElement interface block and HeatFlowRate value type

Suggest the SysPhSLibrary should support Heat and FlowingHeat as conserved quantities with a HeatFlowElement interface block and a HeatFlowRate value type. (Entropy, FlowingEntropy, and EntropyFlowElement are already present but don't cover all thermodynamics cases.)

BTW: The suggested naming, which follows the SysPhS-1.1 naming pattern, is a bit strange in this case because 'heat' always implies flow/transfer.