Return address tags with multiple values as arrays

[rmx90210]

Right now the dor_parcel_id field in the /search endpoint comes back like:

"dor_parcel_id": "016S080346|016S080345",

Any field that can return multiple values should be pluralized (e.g. dor_parcel_ids) and returned as an array.

 "dor_parcel_ids": ["016S080346", "016S080345"],

Empty responses should be an empty array (rather than null).

[Alexander-M-Waldman]

@rbrtmrtn this requires a signature change - should hold off until new release?