Add cache_busting support to document editing

Add a cache_busting boolean option to the Document's to_json and
canonical methods.  If set this will add the Document's updated_at
timestamp in UNIX epoch format onto the end of the page_image_url.
This will prevent browsers from displaying a previously downloaded
document image after it's been edited.

The cache_busting option is only selected by the document viewer's
template if the currently logged in user is allowed to edit the
document.
Remove incomprehensible nested ternary

No idea why/how I thought that was a good idea, perhaps I was attempting to minimize the code changes?
Add p3p header to DocumentsController#show

Move the set_p3p_header method from authentications controller to a
protected method on the application controller so it can be shared
between all controllers who may be embedded in an iframe.

This should provide a solution for issue #39
Merge branch 'master' of https://github.com/documentcloud/documentcloud
Merge branch 'master' of https://github.com/documentcloud/documentcloud
Merge branch 'master' of https://github.com/documentcloud/documentcloud
Save remote document to store after downloading

When a document's source is specified as an URL it was downloaded but
then never saved to the (file|s3) store.  The import action then would
error out later when it attempted to read the meta data from the
original file.
Merge branch 'master' of https://github.com/documentcloud/documentcloud
Merge branch 'master' of https://github.com/documentcloud/documentcloud
Merge branch 'master' of https://github.com/documentcloud/documentcloud
Merge branch 'master' of https://github.com/documentcloud/documentcloud
Add method to set temporarily account's membership

Since the role is no longer directly accessible on the Accounts, it
isn't return by to_json.  For that we need canonical

When an account is updated by an admin, the role is set properly in
accounts_controller, but the returned json doesn't include it and the UI
never updates.

This adds a scoping method to accounts that will temporarily set the
membership to a given organization (if it's valid).  The accounts
methods can then refer to membership and pickup on what membership the
account should be acting under.

If this approach looks good, we can rewrite additional Account methods to
use the @membership instance var.
Move membership setting block to Organizations

Makes the organization be the controlling entity for setting the
current membership.
User current_membership for role
Rename 'Manage Accounts' to 'Manage Organization'

For Admin user only; it's named 'Manage Account' for non-admins.
Add language pref to Accounts & Organizations

Unsure if defaulting in canonicial is best way to go.  Could make it
default to 'en' in migration and set everyone to that?
Organization Settings

Add a language selection sheet to accounts dialog and re-purpose it as
organizations settings dialog, with accounts at bottom.

Language list will be further refined.
large icon should not have been added
Mixin for language support in Backbone Models

A small JS object that can be mixed into a model to provide language
support methods.  Also gives us one space to set the list of languages
we support.
Language editing for accounts and organizations

Is still a bit wobbly, hide/show cycle sometimes hides organization when
it should only work with account