Move Javascript out of the HTML templates and into .js files

This is much clearer and easier to maintain in separate files.
Allow Javascript to look-up if a MapIt area is in Northern Ireland
Factor out PopIt API object creation so it can be reused
Add a missing newline at the end of models.py
Load all political parties from PopIt on start-up
Update front-end for separate party registers for GB and NI
Remove unused imports
We no longer need to use get_party to lookup parties

The parties are loaded as static data in PartyData now, so there's no
need to go to PopIt to check that a party exists or to get its ID.
Update test fixtures for the new party IDs
Use an integer ID for new people, based on MaxPopItIds

Also make sure to update the value in MaxPopItIds after successfully
creating the person.
Correct a couple of typos
Remove an extraneous newline
The party autocompletion is no longer needed, so remove it
Remove a now unused function
Remove an unused variable
Move the static data loading into its own module
Merge pull request #3 from mhl/use-posts-new-parties

Update front-end for new party and person IDs