Fix issue #10948509: Crash in procstats when there is no data

Also make us much better about determining which app to blame for
a particular running process, organize the display of services by
their owning app, apply some new heuristics for deciding what goes
in the process list so that we can still display interesting processes
when we haven't collected pss data for them yet, etc.

Change-Id: I7e87225d3dabc66cf3ff020b5db48401b14aaf47