NumberPicker showing IME when its input field gains focus.

1. The NumberPicker was showing the IME if the input field
   gets focus and hiding it when the the arrows are pressed.
   The leads to a nasty behavior when the input is the first
   focusable and the uses presser an arrow button. In such
   a case the IME shows and hides on every arrow press pushing
   the window content up and down - this looks pretty ugly.
   Now the IME is show on double tap of the input field.

2. The NumberPicker input now by default has an IME action
   done, hence after editing it the IME goes away.

3. The NumberPicker input now clears focus when it gets
   IME action done, so the last picker in a sequence
   does not show selection which is focus driven.

4. NumberPicker was incorrectly detecting double tap to
   begin edit and it was possble to start edit on singe tap
   if the user has double tapped before to start an edit.
   Now double tap detection is using the double tap timeout
   correctly.

bug:6071977

Change-Id: I0ff5a491064e51663b3abec675d839d0a65b986a