API catch up

[mustberuss]

API Changes since PR #27

• The 10,000 row/10 page limit seems to have gone away. Should we warn if the return will be over 1M rows or so?

• Five of the endpoints are now nested under patent/ The easiest thing to do was to have users qualify the nested endpoints but there might be a better/cleaner way? Ex: endpoint = "patent/us_application_citations".

• Removed nber_categories and nber_subcategories endpoints. They were removed from the OpenAPI object but the API still responds to requests.

• location endpoint is back

• The cpc endpoints and their returned fields have new names.

• The new wipo endpoint returns a wipo entity, breaking the singular endpoint/plural entity pattern followed everywhere else.

• The API currently throws 500 errors when all fields are requested from some of the endpoints. I added a skip in test-search-pv.R.

• Paging is completely different. Now the attribute is "after", where we supply the last value of the previous response. This makes having a sort field required, I've added a default sort and deprecated the page parameter. I haven't tried paging with a secondary sort, I'm not sure the API team has thought this through! (what value should "after" have when there is more than a primary sort) See Pagination for the ElasticSearch API (v0.1) here https://patentsview.org/apis/api-query-language#options_parameter