Change from using ItemizedOverlay to just the AccuracyCircleOverlay to show user location

The big pinpoint wasn't desired, and being that we will want to include a GPS location
with accuracy radius in any case, just use that.
Generate new Paint only on creation of AccuracyCircleOverlay, and improve location point

The Paints were being created every draw, which should be avoided.
Also, changed the location point to more closely match what was in the mock
with a solid blue center and white outline.
Feed Location from GPSScanner to Scanner to StumblerService, and finally to MapActivity

Rather than piece out the latitude & longitude, just get the whole location since
we'll need the accuracy, anyway.
Merge pull request #719 from keverets/pin-point

Change to using a pin-point (with accuracy circle) to indicate stumbler's GPS position