remove old person adding code

This should have been removed before. It worked fine on dev, however on
production the JS compilation directly included the new person template
which uses the render method. As the _ extension that supports this isn't
included in the front end build this then caused a JS error which then
stopped the correct new person event firing.

Also fix broken cancel link on new person page

Fixes #440
Custom query support for autocomplete model

This lets you provide a third parameter to 'autocomplete_model' which
can asynchronously return a query object. This will allow us to restrict
the list of auto-completed to include only those that are relevant to
the currently selected post.
Pass selected post's id when autocompleting orgs

This will allow us to filter the list of organization returned to only
include ones that are appropriate for the selected post.
Add custom query for organization auto-complete

Only auto-complete organization which are relevant to the currently
selected post.
Merge branch '418-restrict-posts-listing'
Update popit-api to latest master

This includes the latest code for retrieving a full record without
processing the translations.
Remove the need to enter an invite code
add correct classes for object attaching on org page

add posts and memberships classes to the lists that contain these in
order allow the ids of the related objects to be correctly attached.
Without this the edit button doesn't act on the model and you end up
creating a new model and the delete button doesn't do anything

Part of #406
call destroy directly on posts model for deleting

Becuase posts are a separate model and not nested within the
organization we need to destroy them directly rather than removing them
from the nested collection and then rely on that cascading the save up
to the organization model. If we don't do this then no API call is made
and the post isn't deleted on the server.

Fixes #406