Fires geofence if the device is already in the geofence area.

Process the location of the fence as soon as it is added.

Clarified how the distance to the fence was being used.

Added more debug logs (disabled by default).

Fixed a numerical overflow in the location request if the
distance to the border of the nearest fence was greater
than about 2000Km.

Removed a useless call to request location updates passively
when the geofence manager is initialized.  We have no need
of location updates unless there are active geofences.
The effect of this call was undone the next time the location
request was updated anyhow.

Changed the location request to always request a fastest update
interval of 0 which accomplishes the goal of passively
monitoring all updates.  This does not increase the power
consumption because we are conservative about choosing
a minimum location update interval.  We're simply stating
that the geofence manager is willing to handle a higher
report rate which is very important.

Subject location to a "freshness test" - only use relatively
recent locations for geofence testing.

Run all geofence updates on the handler and avoid making
multiple redundant calls into the location manager when
updating the provider requirements.

Ensure that we update geofences correctly even if we don't
know the initial location of the device at the time the
geofence is created.

Pin update interval value to the range [1m..2hr].

Distance to fence is now distance to fence's border, not
distance to fence's centre.

Bug: 7466334
Change-Id: I28e571ecfc508d5ceb9bb2afcabaaf05abb26369