[Bug 1033339] Fix latest_version in product view.

This is a partial revert of 64d896f1d7524a4b45648a10ee2d99988eb49e83
[bug 766394] Added column for share links.

max_length is 24 characters, which should cover the url lengths
as they grow for years to come.
[bug 766394] Added migration for kb share links.
[bug 766394] Share links now add to database.

They are not generated yet, but there is a base set up for putting
them in the database if the box is checked.
[bug 766394] Generate share links for KB articles.

Share links are generated via bit.lys API, and the configuration
for accessing that API can modified in settings.py.
[bug 766394] Added show/hide share link option.

Added migrations, form element, and now share_links are auto-generated
for each new KB article, but you can choose to hide or show them.
[bug 766394] Fixed styling for share link button.
[bug 766394] Fixed error for showing share link.
[bug 766394] Fix to stop regenerating links.
[bug 766394] Default show_share_link is now False.
[bug 766394] Added check for dev/staging env.

Also editted some styling and safeguards for KeyErrors.
[bug 766394] Replaced show_share_link with logic.

We now only generate share links if the article is in a
category that should have share links generated for itself.
[bug 766394] Removed unused import.
[bug 766394] Fixed template spacing.
[bug 766394] Added migration for  migrations user.

This is the user we should use for data migrations when having
to assign owners/creators to new objects.
[bug sharelink-766394] Share links data migration.

This is a data migration for share links. If the template tag
sharing a link is found in the most recent revision for a document,
we then create a new revision based off the most recent one with
content that excludes the share link.
[bug 766394] Moved short_link generation code.

It is now done with a celery task because it's an API call and we
want it to be asynchronous. Additionally, I added more descriptive
exceptions for any status code responses form bit.ly's api other
than a 200.
[bug 766394] Fixed util reference mistake in forms
[bug 766394] Changed quit conditions.

We now quit the generate_short_url function if either a username
or API key is not found. There was also an update to an error
message.
[bug 766394] Cron job for generating share links.

There is now a cron job for generating share links where they
are missing.