Polish the NumberPicker, TimePicker, and DatePicker based on UX request.

1. Now the spinners in the time and data picker a wider therefore
   easier to interact with, i.e. harder to miss accidentall.

2. Removed the scroll distance cut off user to distinguish between
   fling and change by one.

3. Added visual feedback when the areas the serve as virtual buttons
   in number picker are poked.

4. Removed the coeffcient that was making drap not to be one-to-one
   with the scrolled distance.

5. Added some margin at the top and bottom of the spinners in
   date and time pickers.

bug:6321432

Change-Id: I311c1733d1951b0563209401faa830ca70ec87cb