Display visible GPS satellites

This is a suggestion for a partly fix of #973. I put the "/" to the strings.xml for RTL compatibility.
![gps](https://cloud.githubusercontent.com/assets/3845150/4710017/c9f7c3e2-58a4-11e4-93d0-e31f8c27b999.png)

Sounds good, please file as a separate PR, in case we have to revert either one of the PRs.