remove unused code
fix #1883 measure time in seconds between application_opened and application_closed
put signOut in an AsyncTask and show a ProgressDialog
use the asyncSignOut in WPActionBarActivity
use the asyncSignOut in PreferencesActivity
`NotificationsDetailListFragment` now listens for note changes.

List will refresh if the currently viewed note was changed. Detail view will pop back to list if the note was removed.

Also added a note changed listener, so that `CommentDetailFragment` can be notified when the note changes and update the comment and moderation buttons.
Merge pull request #1894 from wordpress-mobile/issue/1883-application-opened-time

fix #1883 application opened time
Added a null check on `getActivity()`
Merge pull request #1893 from wordpress-mobile/issue/1890-notification-detail-changes

`NotificationsDetailListFragment` now listens for note changes.
don't send BROADCAST_ACTION_SIGNOUT from removeWpComUserRelatedData()
null check mProgressDialog before dismiss and use local context instead of getContext
Merge pull request #1895 from wordpress-mobile/issue/1796-signout-lag

fix #1796 signout lag
Added context null check to reader service, WelcomeFragmentSignIn now uses the application context when starting the service.
Merge pull request #1902 from wordpress-mobile/issue/1898-npe-reader-service

issue/1898-npe-reader-service
Removed mPagerAdapter, now creating new pager adapter when needed and removing previous adapter before assigning to ViewPager
Check for a valid `comment` before moderating.

Hard to reproduce, but I think this could have happened if the button click event was triggered after `onPause()`.
Create the new comment status from within moderate button's onClick().
Merge pull request #1907 from wordpress-mobile/issue/1900-npe-comment-detail-fragment

Check for a valid `comment` before moderating.
Fixed potential NPEs after calling getPagerAdapter()
Merge pull request #1905 from wordpress-mobile/issue/1899-illegal-state-reader-pager

issue/1899-illegal-state-reader-pager