Pie controls: A new way of activation

Based on "Pie controls: Introducing a pie delivery service" this
commit binds the pie controls to the newly created pie service.

Patch Set #2:
* Fixed glitch when displaying the search panel at the lock
  screen.

Patch Set #5:
* Switch Position to com.android.internal.util.pie.Position
* Removed legacy and unused code

Patch Set #6:
* Fixed lock screen glitch, finally!

Patch Set #7:
* Rebase

Patch Set #9:
* Moved almost all of the pie logic to PieController

Patch Set #10:
* Remove window completely from WindowManager when not shown

Patch Set #13:
* Fixed Taichi's bug
* Removed observers in PieView

Patch Set #14 & #15:
* Rebase

Change-Id: I352f198068807694d95699618597d0927da3f324