Add 1.5-layer QG functionality

[navidcy]

It's easy to include a finite Rossby deformation radius in BarotropicQG module. I vote first to clear up BarotropicQG module as implied by #135 and then modify the BarotropicQG module to add such functionality.

pinging @liasiegelman as she's interested and could help us out here.

[liasiegelman]

sounds good to me. I will let you know as soon as my barotropicQG with kdef implemented in the streamfunction runs smoothly

[navidcy]

@liasiegelman, v0.9.0 includes a cleaner BarotropicQG module. Feel free to make a PR modifying it to include finite Rossby radius of deformation. We can then work on it together if you like :)

Perhaps we should change the module's name since it won't be purely barotropic then? What about OneLayerQG?

cc @glwagner

[liasiegelman]

Thanks @navidcy, will do. What about equivalentbarotropicQG for the name?

[glwagner]

OneLayer is probably better than Barotropic anyways! EquivalentBarotropicQG seems good too.

[navidcy]

Does the name EquivalentBarotropicQG include the purely barotropic case k_deformation=0? If so then it's good name. Otherwise let's go with OneLayerQG or SingleLayerQG.

[liasiegelman]

ah yes then it's just barotropic so probably better to stick with your original suggestion.

[glwagner]

"SingleLayer" might be a better complement to "Multilayer" (eg with "OneLayer" we might want "NLayer").