Introduces a new LoaderManager class that takes care of
most of what LoaderManagingFragment does. Every Fragment
and Activity can have one instance of this class. In the
future, the instance will be retained across config changes.
Also various other cleanups and improvement.
Change-Id: I3dfb406dca46bda7f5acb3c722efcbfb8d0aa9ba
c801768e4d