Filter events by area (just pass area via query)

[osfameron]

[osfameron]

Some links:

• http://global.mapit.mysociety.org/
• http://davidcel.is/posts/distance-constraints-with-postgresql-and-postgis/ (squirrels!)
• http://www.postgresql.org/docs/current/static/earthdistance.html (simpler!)

[HakimCassimallyBBC]

First slice:

• add an "areas" table, to contain some info from mapit
• add single (for now) foreign key from event

Omitting for now:

• m2m relationship
• hierarchy

[osfameron]

On review, this appears to be broken in demo. Requires a test-case (I removed the feature spectest in favour of the Geo IP ones) and fix.