Don't set cache name for forum tree data source.

We were seeing a crash in 2.0.3. An example crash is
http://crashes.to/s/b201e295bac. The crashing method is
-[NSFetchedResultsController(PrivateMethods) _preprocessUpdatedObjects:insertsInfo:deletesInfo:updatesInfo:sectionsWithDeletes:newSectionNames:treatAsRefreshes:].

Some searching turned up http://stackoverflow.com/a/14843264, which mentions a
crash in that method, and finds that an undetected invalid cache is the
culprit. Since we only started setting the cache name in 2.0.3, and turning off
the cache is no big loss, it seems worth trying.
Add some Crashlytics logging to figure out crash scraping messages inbox.

Crash is "This NSPersistentStoreCoordinator has no persistent stores. It cannot
perform a save operation."
Fix split view sidebar staying hidden after rotating device.

When rotating the device while some other view controller takes up the screen
(e.g. watching a video), we weren't updating the split view state to consider
the new interface orientation.
Fix dark theme setting in profile view.

Deleted the JavaScript Awful.dark function ages ago, forgetting that the
profile view still used it. Reinstated.

Bonus: rework the profile view controller a bit to make it less confusing.