Feature request: Additional AeroDyn_Inflow_C_Binding routines

[andrew-platt]

The AeroDyn_Inflow_C_Binding interface is missing several routines that will be needed for integration with SEAHOWL. These include:

• Routines to retrieve environment variables
  - [ ] GetAirDens
  - [ ] GetKinVisc
  - [ ] GetSpdSound
  - [ ] GetPatm
  - [ ] GetPvap
• GetWindVel - provide the same thing as the IfW_C_Binding interface does
  - Include logic for when IfW data is accessed by pointer to external instance (SEAHOWL may do this)
• GetAeroNodePosOri - retrieve all positions and orientations of aerodynamic nodes (needed for SEAHOWL)
• Tower interface routines for tower loads

Some of these features will take longer to implement than others, so they may need to be on the v5.1.0 release instead of 5.0.0