Fragment and PreferenceFragment and FragmentManager, oh my!

- Introduce FragmentManager public API, for all Fragment management
  needs.  Will in the future allow the removal of the (growing number
  of) fragment APIs on Activity.

- Fragment now has a concept of arguments.  This can be supplied
  immediately after creation, and are retained across instances.

- PreferenceActivity now has an API to have it update its headers (note
  not tested).  Headers now have arguments.  Keys for controlling
  when PreferenceActivity shows at launch have been added to the SDK.

- Fixes to back stack handling and state saving/restoring.

Change-Id: Ib9d07ae2beb296c4eb3a4d9e1b3b59544675e819
9 files changed