HALO tweaks and Fixes

-Draw status bubbles only when required (performance)
-Ninja level +1 (disappear if empty, only persistent or pinned apps are present)

(cherry picked from commit c7316cd307b6f1feaf56248fe4ca4c211007456a)

Conflicts:
	packages/SystemUI/src/com/android/systemui/statusbar/halo/Halo.java