Let GroupMembersFragment control actionbar, menu and more.

* Create mActionBarAdapter from GroupMembersFragment and remove
  mActionBarAdapter from GroupMembersActivity.
* Move creation of group-related menu to GroupMembersFragment.
* Move the following listeners to GroupMembersFragment:
  - ActionBarAdapter.Listener
  - MultiSelectContactsListFragment.OnCheckBoxListActionListener
* Move UpdateGroupMembersAsyncTask a new class.
* Remove mGroupMetadata from GroupMembersActivity and get it from
  GroupMembersFragment instead.
* Remove GroupMembersListener, since the actions can be done within
  GroupMembersFragment now.

Bug 30944495

Change-Id: Ie6a7c51afecdc67f953f185369f64f2192c46bc1