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?
Merge remote-tracking branch 'upstream/master' into cache_busting
Memberships should be destroyed with their account or org.
More sysadmin rake tasks & more testing out pdftailor over pdftk.
update AMI id.
Update the search_embed build.
Disabling redaction ui.
Import, Public, Search Controllers
Forgot to add soffice to the list of things to kill.
Updated wording for document error message

Point out that redaction need to be checked on document and PDF if the
document is in error state.
Re-enable redaction UI

Now that we've got an updated error message in
commit 7371869a87766bf6372f3c9cc946974464d4d9b3 it's safe to re-enable.
Disabling redaction ui.
Disable redactioning once again.

Let redactions still occur if the shift key is pressed.  This
will allow us to test out fixes for them.
Windows fix for redactions bypass shift key

On Windows holding the shift while clicking the redactions tool link
toggles redactions opens & shuts very quickly, seems like the event is
delivered twice. Worked fine on OSX though.  As a work-around,
just open the tool explicitly
Merge branch 'cache_busting' into upstream_master

The redactions were taking place but the images were being cached, making it appear that they did not.
Set Annotation Editor's _kind instance var

This is pretty dirty to set a clearly private instance var, but is a
temporary hack for us to semi-enable redactions while we test bugfixes.
Return thumbnail_url with cache-busting time-stamp

This way the thumbnail will update once the document processing is
complete, instead of the browser caching the old thumb-nail.
Keep redaction tool open regardless of keydown
Only append cache_busting timestamp on public docs

Private document's thumbnails come from S3 with time-limited url and are already unique