Improve flexibility ZoneHVACLowTempRadiantVarFlow (and ConstFlow): coils and surfaces

Couple of things I'd like to see:

Ability to use a heating coil, a cooling coil, OR both

Overload/modify constructor of ZoneHVACLowTempRadiantVarFlow to not only except both a cooling and heating coil (source here). I'd want to be able to initialize it with either a cooling coil, a heating coil, or both.

Flexibility to define surfaces

I like the fact that the user can use "Radiant Surface Type" to let OS decide to include it in a Floors/Ceilings/CeilingsAndFloor/AllSurfaces.

But what If I actually only want to put it on a given surface (say a wall or two), I can’t right now.
I guess for now one way around that is to put “All Surfaces”, and only have a construction with an internal source assigned to said wall. But it doesn’t seem terribly flexible. As I understand, in some cases you might want to explicitly model different circuits, with this workaround you can't do that.

Therefore a method setSurfaces(std::vector<Surface> surfaces) would be nice.

That would need refactoring of the object to include isSurfaceDefaulted(). Perhaps radiantSurfaceType could include “Manual” as an option, and if you call setSurfaces() it’d change that to Manual. If you switch back, it'd call resetSurfaces() in the process.

The same comment applies to ZoneHVACLowTempRadiantConstFlow.
I'd also add that I don't see any reason the constructors between the const flow and the var flow would be different. The Const flow shouldn't except a hydronic tubing length in the constructor. In both the Const Flow and Var Flow, this field is auto-sizeable.