generic way to track last seen activity - requires GET_TASKS permission
manual tracking of last seen activity
add post editor to tracked activities
add login screen to tracked activities
remove unused util file ActivityUtils
catch IllegalArgumentException in case settings field for last seen activity is bogus
move class ActivityId to its own file
Merge branch 'develop' into issue/1690-track-last-seen-screen

Conflicts:
	WordPress/src/main/java/org/wordpress/android/ui/posts/EditPostActivity.java
Merge pull request #1691 from wordpress-mobile/issue/1690-track-last-seen-screen

fix #1690 track last seen screen in analytics