Changed quiet hours and default reminder time settings to use TimePicker instead of list arrays

So, 
I changed the three reminder settings to use a TimePicker instead of the MultilinePreference like they did before. Now you only need the arrays containing the AM/PM hours for legacy reasons. I tested the new settings on two emulators (2.3.3 and 4.4) and on a tablet with 4.2 and they seem to work as expected.
I also added the piece of code to migrate from the old settings to the new ones. I did some minor tests to see if it works well and it seems ok but I'd say you have to test the migration part as well just to make sure.

Hope it's ok. :)