Permit setRetainInstance(true) on nested fragments, framework edition

Save arbitrarily nested fragments across config changes as
nonconfiguration objects. This permits the use of retain-instance
child fragments as arbitrary opaque dependencies within other
fragments.

Change-Id: Ia6640b76cfcf7ec28ba252628957a0c14863e957
(cherry picked from commit 7466be66263d5ebffb786ea402d9ed6e36c254f0)
8 files changed