Fixes 'Next Timed Start [nn:nn:nn]' encoding

Replace QString.sprintf by concatenations to preserve encoding 'Next Timed Start (and french accents).

**Before**

![before](https://cloud.githubusercontent.com/assets/24570/4345427/67796912-40cd-11e4-9c47-7d279a43d482.png)

**After**

![with](https://cloud.githubusercontent.com/assets/24570/4345428/77725360-40cd-11e4-81c7-8ecf420b6d85.png)