Bug 1049569 - Sanitize e.me app url results. r=kgrandon

e.me app result urls often miss the trailing slash. Sanitize them so we get better bookmarking behaviour in the system browser.
A longer-than-expected conversation on IRC leads me to think that although the apps.length access would be cached anyway, it's not certain that this optimisation *won't* make a difference, so added it anyway. ftr, I'm not keen on it wrt readability though...