Add package information to association sources.

This is often known by the system, though not always.  But when
we do know it, it is really useful to maintain that info so we can
do queries like "give me all of the associations that package X is
involved with".

Bug: 121146315
Test: manual
Change-Id: I0dd7aeb9147ecfd65a510d3b2a8bb4a0fbab57e3