Battery stats: more events, fixes.

Add new history events for top application package and
foreground application packages.

Doing this involved a fair amount of improvement to history
events.  The event code is now separated out to have "start"
and "finish" identifies, and we use that to now keep track
of which events are active.  With that, when resetting the
stats, we can spit out all of the currently active events at
the front of the new history.

Also fixed some problems when I re-arranged the history delta
int bits that were conflicting with the packing of the battery
status bits.  These packing structures are changed to work
together correctly.

Change-Id: Ic8b815060dd8a50ff4a0a209efc2e1044215cd88