Map view work: GPS location, Observation points, and MLS locations

This is the appearance showing the GPS location in blue, the observation points in green, and the MLS locations in red (attached to their parent observation points with a line).
Also shown is the "locate me" button in the lower left.

![screenshot_2014-09-09-19-35-55](https://cloud.githubusercontent.com/assets/5495083/4210943/579fcf88-387e-11e4-8988-3cc26d9cbc0e.jpg)

The map view fixes addresses issues: #733, #750, #763, #765, #706

The instance count violation was originally issue #7, it recurs from time to time as we accidentally add code that keeps a reference to an activity.