replace hasActivity() by isAdded() (or isVisible() in a specific case: ReaderPostPagerActivity.java)
Merge branch 'develop' into issue/1565-remove-hasactivity

Conflicts:
	WordPress/src/main/java/org/wordpress/android/ui/stats/StatsBarGraphFragment.java
Merge branch 'develop' into issue/1565-remove-hasactivity
Merge pull request #1650 from wordpress-mobile/issue/1565-remove-hasactivity

fix #1565: replace hasActivity() by isAdded()