Homescreen widget support

This addresses #983 and to some extent #476. 

This commit would allow the addition of a simple widget to the user's home screen that currently displays the number of WiFi access points and cell towers it sees. These text views can be easily modified to display the user's rank on the leader board or the number of reports pending. 

Clicking on the icon toggles the service on and off.

![When the service is on](https://cloud.githubusercontent.com/assets/5414885/5239842/19759596-78a5-11e4-830e-398fbd777bd2.png)

![When the service is off](https://cloud.githubusercontent.com/assets/5414885/5239843/1975f720-78a5-11e4-8ea9-1936ea42b697.png)

Has been tested on Android 5.0 and Android 2.3.6