[ENH] Support versioning of surrogate models

[duetosymmetry]

In vacuum call today, @keefemitman and I were discussing that it would be nice to be able to publish a surrogate model and later add improvements to it. In a sense this can already be supported by just appending version strings into the name of the model, e.g. "model_v1", "model_v2". But, for the end user it would probably also be nice to just be able to use whatever is the latest version of some model, so simply "model" for whatever version is highest.