FIX: 1380091 Use locale time

Fixes Bug 1380091

Now we display the time with a format appropriate to the chosen locale
Please note: 
QLocale() does not construct a system Locale. It construct the default locale, which is changeable with setDefault(). We may use this call somewhere in mixxx.cpp to have the consistent number formats to the selected language. But be careful, because this may change a lot elsewhere.