Theme implementation fixes for PM list, vertical tab bar controller.

The tab bar controller wasn't telling its non-child view controllers about the
theme change. The PM list wasn't theming its cells. Plus various little
formatting changes.
Dark theme posts view top bar and toolbar.
Better match iOS 7 keyboard key style in compose view.
fixup keyboard buttons
Fix private message compose view getting stuck open after restoring state.
Full-width navbar on iPad with dividers between tabs and master/detail.

And lighten up on the black a bit in the dark theme.

Also get rid of the never-called
-[AwfulExpandingSplitViewController tabBarItem].
Try to crash when inserting a post with a nil postID.
Be less stringent about submitting the reply form.

I guess we can't assume formkey and form_cookie parameters. Use 'em if we got
'em, otherwise press forward.
Don't insert a newly-created post if we don't know its ID.

Otherwise our object store will never save :-(
Fix editing, replying, and posting when "Hide Google/Amazon Search Bars?" is set to "no".

We were scraping the wrong form, as I'd naively assumed the first form was
always the right form. Now we're looking for parameters we expect to find,
which seems less fragile in general.
Update thread's last post date/user when scraping last page.
Fix loading pages that are not encoded as win1252.

Sometimes I guess SA's response headers don't lie?
Don't crash when locating posts.

Passing a string where a post was expected is not helpful!
Open profile links within Awful.
Indent subforums in forums list with a horizontal line.

The line grows as we descend the hierarchy.

Indenting with whitespace didn't work very well. Either the indent squished the
forum name too much, or it was so small that it looked accidental. Adding a
thin line restores the feeling of intent.
Update Crashlytics.
Consistently present/push view controllers.

Browser and profile view controllers should be pushed on iPhone, presented on
iPad.

I also took the opportunity to clean up some boilerplate and fix some
formatting.
Shush GRMustache.
Stop pretending that a settings did change notification ever mentions more than one setting.
Add new expand/contract icons for iPad.