Update popit-api to latest master

This includes changes to do with removing slug handling
Fix routing to person/organization images

This broke because the ':id(*)' pattern only works if it's the last
dynamic segment of the url. This switches the view and delete image
paths around so that the id of the organization or person comes last.
fix html escaping bug on instance description page
merge
Merge branch 'ui-refresh' of git.mysociety.org:/data/git/public/popit into ui-refresh