Add a `set` parameter on `/resources` to allow NWBib queries
Update API doc index page for `set` parameter and restructure page

Remove endpoint-specific parameters from the main table and set up
a table for the `/resource` parameters (`author`, `subject`, `set`)
Add sample API usage to download all NWBib data (closes #117)
Tweak hit processing for multi-id values (list of maps)
Tweak sample application for larger data sets

Get 100, not 50 documents per request and wait 1/2 second, not one
Always wrap the JSON result into a `@graph` element
Update queries and views for `@graph` wrapping on all results
Simplify hit processing with JSON
Merge pull request #129 from fsteeg/issue-117-nwbib

Provide API to access NWBib data
Add *.json suffixes to test data files to fix GitHub language stats

GitHub thinks these files are Perl and PHP