Move all the functions in ui.c to be members of a ScreenRecoveryUI
class, which is a subclass of an abstract RecoveryUI class. Recovery
then creates a global singleton instance of this class and then invoke
the methods to drive the UI. We use this to allow substitution of a
different RecoveryUI implementation for devices with radically
different form factors (eg, that don't have a screen).
Change-Id: I76bdd34eca506149f4cc07685df6a4890473f3d9
