bootanimation: performance enhancements

This patch implements two simple performance enhancements, which
might benefit devices. They are completely opt-in by setting
the following variables.

  * TARGET_BOOTANIMATION_PRELOAD: will preload the bootanimation
    zip to memory; this is handy on devices where the storage
    might be slow. By preloading it, we get quick access to the
    zip file, and the animation doesn't stutter.

  * TARGET_BOOTANIMATION_TEXTURE_CACHE: allows maintainers to
    force texture cache on/off.

Also fixes the sign warnings related to int / size_t comparison

Change-Id: Ie92d1b0aa90b43ba39c368a2a33657a60c3a64b5
improve swipe between pull down animation

this greatly improves both animation and function of swipe between screens
it allows for a hold on the animation and also freezes the notification panel
to do: add fling animation so it keeps spinning?

Change-Id: I04c4332d6f3678eb331f52d90e0db4c3fe414454

Conflicts:
	packages/SystemUI/src/com/android/systemui/statusbar/phone/NotificationPanelView.java