Move aggregator to its own package

... so that methods used only by ProfileAggregator don't have to be public.

And fix some method visibilities that don't make sense.

Needed to change the bogus ID in PhotoStoreTest; otherwise moving the
aggregator test will make this test fail for some unclear reason.

Bug 6118852

Change-Id: Ic0c022cbf50128f40c70559c1a7cf8e2a6c06fc8
21 files changed