Attaching the timepicker to the input instead of the sorrounding div didn't
turn out as expected. Therefore, I used the same mechanism for DOM attachment
and lazy initialization for the timepicker like for the datepicker.
Instead of trying to load the CSS through webpack and some JS voodoo, it's
a lot simpler to just include it via the normal base theme CSS. This works.
In addition, I noticed that there is an easier way to read the current locale.
No need to do this twice via different ways.
This closes#516.
MichiK