Distance indicator in Portalview

Added a distance indicator in the portal view for optimal positioning and resonator deploying. (Sometimes GPS is changing while in portal view and your resonators aren't at optimal range)

![screen shot 2013-07-03 at 7 56 32 pm](https://f.cloud.github.com/assets/55079/745039/32c2af60-e40a-11e2-928a-10a915fb316a.png)
![screen shot 2013-07-03 at 7 56 41 pm](https://f.cloud.github.com/assets/55079/745051/4cc2d174-e40a-11e2-9033-7796031bfde6.png)