Allow additional query parameters to be specified to get_search_url
Give some variables better names
Make sure 'identifiers' can be set and preserved

This is important because we use it to store the old YourNextMP ID from
the imported data.
Add a comment (hopefully?) explaining get_person_data_from_dict
Add a field for the party PPC page's URL

These have quite a bit of information on them, and they're typically the
source for our PPC data, so we should make them available.
Add manually matched PPCs
Add a command for importing PPC data

If it thinks it's found a match for the PPC, it'll ask the user whether
they're actually the same, and record that decision so it doesn't have
to ask again.