[bug 1030348] Fixes issue with Topic selection Dropdown
[bug 971782] JS fix for data bucketing (weekly, monthly).

The bucketing implemented in Rickshaw does not like missing data
for any dates. It wants explicit 0s. This zero-fills all the
dates.
[bug 987337] Show topic descriptions on topic pages.
[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.