Add improved alert/error popup. Fix hide-read-posts. Fix thread actions dropdown+sharing.

Added AwfulFragment.displayAlert() functions, they take a title, subtext (optional), icon (defaults to ! icon), and display time (default 3sec). It looks similar to the iOS loading/alert dialog. Basically, replace any calls to Toast.makeText with this, you don't even need to check for activity!=null like you have to with Toast.

Also fixed bugs introduced with recent changes:
-Bookmark shortcut opens the right section now.
-Hide-read-posts works again.
-Thread action dropdown and share were broken due to ABC changes, fixed now.