Don't read settings constant on every touch event for double tap to sleep

Change-Id: I5108d24b7006e518926ce02d1a5eae8da406df8f

Conflicts:
	packages/SystemUI/src/com/android/systemui/statusbar/phone/PhoneStatusBar.java
Memoize memory class lookup methods

These methods are commonly accessed.  Lets make sure we only do systemproperties lookup
once since these values aren't changing afterwords.

Change-Id: I77802ed367e4180f4d97e6abbd98170e6cf7a0d4

Conflicts:
	core/java/android/app/ActivityManager.java