Support APIs that return data underneath a key

Problem/Motivation

I don't think this is currently possible - if it is, how would I do it? - but a lot of datasets seem to return data under a key. A silly example would be https://rickandmortyapi.com/api/character/ where the info key returns information about the results and the actual results are under a results key.

Steps to reproduce

Try to create a remote select using the https://rickandmortyapi.com/api/character/ result set, with the character ID as the value and the character name as the text. Note that there doesn't seem to be any way to specify that these are contained within the "results" key, so this is not possible.

Also note that if you try to use values that don't exist in the API that the module throws several errors rather than handling them gracefully.

Proposed resolution

Create an additional optional field for "base key" (or whatever wording makes the most sense). When that value is provided, use that as a basis for where to look for the specified value and text options.