HALO Style revamp

- speech bubbles are centered
- number batches are roundand simplified, same color as in g+
- markers appear as dots above the bubble
- hiding and dimissing triggers text hints
- couple of bugfixes

WARNING: some of the drawables are good for xhdpi only for now and must
be scaled down for the other resolutions

Change-Id: Ib656664f6f8c42b747df18d65d1e3fb40cb7480c

Conflicts:
	packages/SystemUI/res/values/strings.xml