More work on device idle mode and other power stuff.

Add idle mode support to the alarm manager.  Introduce
a new concept of flags associated with alarms to tell
the alarm manager how to treat the alarm -- they allow
everything from the alarm that will bring us out of idle
mode, to alarms that are allowed when idle or should
also bring us out of idle.  The standalone boolean is
now also a flag.

(Note there is currently no protection from user space
setting the flags however it wants; I will be working
on that in a follow-up change.)

When in idle mode, the alarm manager pushes all alarms
that shouldn't execute during that time over to a
separate list that is not executed until out of idle.
To help with this, I reworked a bit how Alarm objects
are managed, so that when rebatching or moving between
lists we don't have to allocated new objects but can
just use the same existing instance.

Also tweaked the sync manager to deal with idle mode,
which currently just means doing the same thing as when
low on storage -- turning off sync.

Add new ACTION_CHARGING and ACTION_DISCHARGING broadcasts
that apps can listen for to know when the device is actively
charging and discharging.  These are better than the old
POWER_CONNECTED and POWER_DISCONNECTED ones because we only
report charging when we actually see that there is enough
power being provided to charge the battery (and will report
discharging if there is not enough power).

The job controller uses these new actions for scheduling
jobs that want to run while plugged in.  Removed the
"stable charging" stuff while doing so, since the new
charging state serves as an even better signal for that.

Introduced two new process states: FOREGROUND_SERVICE and
TOP_SLEEPING.  This will allow us to treat foreground services
specially (such as still allowing network access to them for
background music playback) while not mixing them together with
whatever happens to be the top activity while the device is
asleep.

Also some other small cleanup here and there.

Change-Id: I7a9808b578bad6f50deb8e1baf919298512a0d3a