HALO: new drawables for hdpi and mdpi

- scaled down the xhdpi drawables properly for hdpi and mdpi
- removed some old and unused halo pngs

Signed-off-by: Dan Trifan <jimsth@gmail.com>

Conflicts:
	packages/SystemUI/res/drawable-hdpi/ic_launcher_clear_normal_holo.png
	packages/SystemUI/res/drawable-hdpi/ic_notify_halo_normal.png
	packages/SystemUI/res/drawable-hdpi/ic_notify_halo_pressed.png
	packages/SystemUI/res/drawable-mdpi/ic_launcher_clear_active_holo.png
	packages/SystemUI/res/drawable-mdpi/ic_notify_halo_normal.png
	packages/SystemUI/res/drawable-mdpi/ic_notify_halo_pressed.png

Change-Id: I90cd8918f6b000cfb4523c6b455b77efa958f631