Alternative timepickers: Use select combo boxes

This issue is spun off from #233047: Switch to using Vega timepicker. The idea is to implement this mockup from @Noyz:

https://skitch.com/jeff.noyes/fpmwh/adobe-fireworks-cs5

Probably, this would replace the current "none" option for the timepicker (which just uses a textfield for the time), since people who are using a nice popup calendar are unlikely to want to combine it with a plain old textfield for the time - the contrast in how you use them is pretty huge :)

However, it could also become a separate option instead.