Add Organisation model with M:M relationship to User
Add a rake task to fetch organisations from Whitehall

This task fetches the current list of organisations from Whitehall
(which is the canonical source for organisations), creates new ones
in the Signon database and updates any which have changed.
Add an index page for Organisations
Add UI for editing user membership of organisations

This needs to be hidden behind a feature flag until Signon becomes
the canonical source for user membership of organisations. Until
then, these relationships should be edited in Whitehall.

Abbreviations need to be displayed as well as names so that users can
find organisations by typing the abbreviation, but the abbreviation
needs to come after the name because not all organisations have
abbreviations, and some are long. The abbreviation also needs to have
a space before it for finding by typing to work, but putting it in
parentheses with spaces looks odd, so it is separated from the name
with a | when it's used.
Remove trailing whitespace from 3 files
Use em-dash to separate name from abbreviation

This is a clearer separator than a pipe in the context of the
organisations membership editing box.
Add flag disabling editing of user memberships of organisations

The 'View Organisations' page is still visible to admins, but the
user edit form doesn't allow editing of organisation membership.
Remove closed_at datetime from organisations

Not all closed organisations in Whitehall have a closed_at datetime
set (2 out of 4 do have it) so it's not reliable for finding closed
organisations. If we do want to provide different behaviour in future
for closed organisations or those which are exempt from transitioning
to GOV.UK, govuk_status from Whitehall is the most accurate available
source for that information.
Change separator from em dash to en dash
Add two explanatory comments
Schedule daily cron job to fetch organisations

This is done with Whenever, and capistrano will update crontab on
deployment.
Simplify handling of organisation_ids in user form

Let Rails handle it via mass assignment rather than doing it manually.
Merge pull request #95 from alphagov/organisations

Organisations from Whitehall