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.
save birth and death dates

also tidy up the code a chunk to remove duplication, handle edge cases
of removing dates requiring a null to be passed.
Rudimentary handling of errors.
reset edit field values when canceling edit

when the cancel button is pressed it should reset the values in the edit
fields to their original values which it does by looping through them
and pulling in the values from the view equivalents
fix html escaping bug on instance description page
merge
Merge branch 'ui-refresh' of git.mysociety.org:/data/git/public/popit into ui-refresh
darker greys
people and organization icons on homepage and empty entity listing pages
new person and organization placeholder images
fix other names styling in edit mode
better error message when person/organization name is empty
generic backbone ajax error message
fix mis-aligned close button on login success message
hide edity actions on homepage for anonymous users
homepage whimsy
new person edit page

cut down version of the edit page for initial person creation
delete a person

with basic built in JS confirmation dialog
display login button on new person page if not logged in
use backbone error dialog for delete errors