Rename GroupMemberPickerFragment rawContactsIds

... and all associated ARG and KEY constants to
contactsIds, since that's what it really is. Also

* Share the selection clause between GroupMetaDataLoader
  and GroupListLoader -- we were inconsistent in filtering
  out auto add and favorites groups.

* Remove unsued groups methods:
  - GroupMemberPicker.Listener#onGroupMembersSelected
  - GroupUtil#bindPhoto

* Remove some obsolete comments, fix some others

Test: Manually create and edit editable and read-only groups

Change-Id: I9607225d1a61f8673b7d1461149ae30e253c781d