Search for organizations as well as people

Uses the API internally over HTTP as it's much cleaner than trying to
use it directly in code. Still needs to handle results with more than 30
matches.

Fixes #476
update popit-api module to version that has image upload

Update the API to be able to accept image uploads and also to update
image properties

Fixes #214
correct membership tense

Handle cases when we have a start and an end date to prevent things like
current memberships using 'will be a member of'

Fixes #663
add alternative image URL to match API schema

The API uses a different URL scheme to identify images so add an
alternative one for the UI so the two can match up.

Also update shrinkwrap to point at the version of the API that uses the
same URLs

For mysociety/popit-api#84
Pretty print json in production

This makes it easier to read in the browser when you don't have a json
prettifier extension installed.
Add a link to users PopIt instances