[1/2] Base: Network traffic indicator

Preview: http://i.imgur.com/ssTi6pB.png
Improve scrolling cache

Scrolling cache helps make short scrolls/flings smooth but will
cause stutter when long flings are made. This patch disables
scrolling cache when long flings are made.

This patch also fixes a related bug where scrolling cache will
not be enabled properly when transitioning from flinging to scrolling.

Patch Set 2: Calculate threshold based on maximum velocity (Sang Tae Park)

Credits: Pawit Pornkitprasan

Change-Id: I1fdbaad92263c9f983a32900e74eba1f0367902b
Signed-off-by: Arham Jamal <arhamjamal@gmail.com>
Revert "remove navigation bar customization"

This reverts commit 4b58b80587a3e562bcc516940c02c8435a417541.

Conflicts:
	packages/SystemUI/res/values/ras_strings.xml
	packages/SystemUI/src/com/android/systemui/statusbar/phone/NavigationBarTransitions.java
	packages/SystemUI/src/com/android/systemui/statusbar/phone/NavigationBarView.java
	packages/SystemUI/src/com/android/systemui/statusbar/policy/KeyButtonView.java