PL-6 Generalize the Search API fields

[Kbentham]

https://palantir.atlassian.net/browse/PL-6

This module splits out the Search API Fields into a new module search_api_field_map. Can be tested using the demo site we have set up. See PL-6-generalize-search-api-fields for more information.

[froboy]

As suggested on the ticket, this should include two modules: Search API Mapped Field (search_api_mapped_field) and Search API Mapped Terms (search_api_mapped_terms). These will eventually go into a new repo entitled Search API Mapped (search_api_mapped) (not sure about this name). The new module should include a suggestion that it's recommended to use in tandem with search_api_federated_solr.

@Kbentham please move the submodule to the new repo, https://github.com/palantirnet/search_api_field_map and ignore the above about splitting fields and terms. Just keep it all together.

[froboy]

This isn't directly related to the fields implementation so it should stay in search_api_federated_solr.

[froboy]

I think https://github.com/palantirnet/search_api_field_map should be added as a dependency to this module.

[froboy]

@Kbentham Why isn't this file removed? Isn't https://github.com/palantirnet/search_api_field_map/blob/master/src/Plugin/search_api/processor/MappedFields.php the same?

[Kbentham]

It is the same I have removed the file.

[froboy]

@Kbentham in testing I noticed that some of the fields (title, image) aren't getting rendered on the page here. It looks like https://github.com/palantirnet/search_api_federated_solr/blob/master/search_api_federated_solr.module#L76 needs to be updated with the new field names. That should... i think... still stay in this module though, as it's necessary for the react things, but not necessarily other uses cases.

Current data in solr (on this PR):

"sm_federated_image": [
  "http://federated-search-demo.local/sites/default/files/styles/search_api_federated_solr_image/public/mushrooms-umami.jpg?itok=2-j6RNl0"
],
"sm_federated_title": [
  "The umami guide to our favorite mushrooms"
],

Desired data (from #40)

"ss_federated_image": "http://federated-search-demo.local/sites/default/files/styles/search_api_federated_solr_image/public/mushrooms-umami.jpg?itok=YKyunezh",
"ss_federated_title": "The umami guide to our favorite mushrooms",

[Kbentham]

@froboy I fixed the issues you found.

[froboy]

@Kbentham I generalized that statement, and it should work for other fields if they exist now. Thanks for your work, this looks good now.