Restores QuickPress shortcut functionality. Fixes #319.
Removed unused imports.
Start the WelcomeActivity instead of NewAccountActivity when no accounts are found when adding a QuickPress shortcut.
QuickPress fixes:

 * Show a toast error if the QuickPress blog was removed/hidden.
 * Added check to post editor that ensures there is a valid blog.
 * Changed WordPress.getCurrentBlogId() and WordPress.getCurrentBlogAccountId() to return -1 if currentBlog is null.
Merge pull request #417 from wordpress-mobile/issue/319-quickpress-fix

Issue/319 quickpress fix