NYPL core objects async refactor

[charmingduchess]

Update D API to use new v3 nypl core objects which is async.

• add load_nypl_core which prefetches the nypl core data in app.js
• export the values that are preloaded, with an empty object default to avoid reference errors in the case of something going awry.
• update all references to nypl core mappings to use new syntax
• update a test to use before for const declarations

[nonword]

Looks right, but don't see the package*.json updates

[charmingduchess]

original failed tests are from before i had pushed the new tag up for nypl-core.