compact view: give link urls "may-blank" css class

makes external links open in a new window when the user preference is enabled,
like non-compact view

Closes #1160.
Allow admins to access deleted user pages by name
Add body property to Link

This is mostly for convenience, since there are quite a few places where
we need to do a check similar to:

    if isinstance(item, Comment):

to determine whether the item's "text" will be in .body or .selftext.
This will allow us to just always use .body regardless of type.
Update nonrevenue status list for gold
Use parent's author as "to" user for mod replies to modmail PMs.
install-reddit: Add libpcre3-dev for traffic scripts.
Add pixel and click redirect server.
validator: Protect from ValueError in VCommentIDs.
Prefs: allow defaulting to new window opens

In general, non-power users tend to not open links in new tabs.  This provides
problems for sites like ours, since we end up with a very high bounce rate -
people click on a submission link, end up on some other interesting site, and
forget all about how they got there.  If that link instead opens in a new
window (tab), that problem is solved.

This is a pretty common behavior on link-aggregation sites, eg Google News.

We definitely don't want to change this for existing users, because that
creates a very confusing change.  Additionally, we're not sure if we will want
to keep this around for everyone, so rather than change the default and
backfill preferences, we're just setting it for anonymous users and new user
registrations - wrapped in a feature flag for easy alteration.
Modqueue: add reply button to comments

[A suggestion][0] from /u/rotorcowboy.

`printablebuttons.html` contains logic that supresses the reply button for
comments that show up on profile pages.  This appears to have incidentally been
included for the modqueue, per 0fe8f70 and prior code, so I just removed it and
massaged a few other things to make everything work.

This also adds comment reply capabilities to the various modqueue-like subpages
(reports, spam, edited).

[0]: http://www.reddit.com/r/ideasfortheadmins/comments/2ju3dg/add_a_reply_button_to_comments_in_the_modqueue/
New windows pref: disable default-on for phones

See 0b7deff for some background.

This ends up being particularly annoying on phones, so we're changing the
default back for them.  An overall revert or an inclusion of tablets are both
stil in the cards, but for right now we need to fix this.

This affects both the desktop site and .compact.

@umbrae gets the credit for writing this; I just tested it and am committing.
Add hook for self-post/comment edit
Fix handling nonexistent welcome message templates
Fix imgur check for disabled domain listings

The current method of checking whether the domain is from imgur for
disabling vote listings (and displaying the notification about them
being disabled) is slightly incorrect, and causes (generally spam)
domains like iimgur.com or 1imgur.com to get caught as well.

This changes to use the is_subdomain() function from utils to prevent
false positives from the check.
Clarify blank score notes in user preferences

Changed ambiguous 'blank for none' to the more descriptive 'leave
blank to show all (submissions/comments)' for the score thresholds
Fix mixed content

Mixed content was causing https errors.  Needed to make sure image
previews were included as protocol relative.
Sanitize translation-specific CSS
Add JQueryResponse.set_text for when set_html isn't correct
websafe() the output of _() if it's to go go through unsafe()
Make sure taglinetext and updated_author are escaped