Simplify parliament API scripts.

Remove much-repeated code, factor behaviour into classes.
Use people IDs to not output information twice.

This script loops through member IDs, but we only want to output the
data once per person (and it doesn't matter which member ID is used, as
the import script immediately matches to person ID).
Fetch right member based upon date.

Otherwise if two members share a parliament ID,
it would always take the first one.
[NI] Update scraper to use API to store JSON.