More procstats work.

The historical data is now a more central part of the stats.
When a checkin happens, the data is not deleted, just marked
as checked in so we can continue to access it.

The default procstats dump is now a new "summary" mode that
shows a more useful set of data for all of the running processes.
By default the current and all committed states are shown; you
use "--current" to only show the current.  Use "--details" to
get the previous more detailed data (which now includes detailed
process data like the per-package data).

Also tweaked uid printing to be a little more compact.

Change-Id: I5414ea7c07134ebd5dc83f6f7b9f6e30151eda85