Rework resolve method #52

As I mentioned in #22 (comment), I'm really not confident in the design of the resolve method, but I don't think it makes much sense to solidify it before farmOS/field-kit#190 is completed, so I can be sure how it will work in practice.

I suppose the most immediate concern for now is, if I anticipate major changes to this method, should I remove the documentation and/or the implementation I have now?

In the course of framing that question I think I've made up my mind... It needs to be removed; there's really no good reason to keep it.

So I've deleted the implementation, the docs and the tests for now and can revert the commit (195b3f0) when I'm ready to revisit this.