SystemUI: Vector drawables for data activity resources

Also include a transparent 'no activity' version to avoid
relayout requests of the ImageView because of size changes.

Change-Id: I0aee41f145b946c79c6bbb2a21954259ebd5f873

Conflicts:
	packages/SystemUI/res/drawable-hdpi/stat_sys_signal_in.png
	packages/SystemUI/res/drawable-hdpi/stat_sys_signal_out.png
	packages/SystemUI/res/drawable-hdpi/stat_sys_wifi_in.png
	packages/SystemUI/res/drawable-hdpi/stat_sys_wifi_inout.png
	packages/SystemUI/res/drawable-hdpi/stat_sys_wifi_out.png
	packages/SystemUI/res/drawable-mdpi/stat_sys_signal_in.png
	packages/SystemUI/res/drawable-mdpi/stat_sys_signal_inout.png
	packages/SystemUI/res/drawable-mdpi/stat_sys_signal_out.png
	packages/SystemUI/res/drawable-mdpi/stat_sys_wifi_in.png
	packages/SystemUI/res/drawable-mdpi/stat_sys_wifi_inout.png
	packages/SystemUI/res/drawable-mdpi/stat_sys_wifi_out.png
	packages/SystemUI/res/layout/signal_cluster_view.xml
	packages/SystemUI/res/values/arrays.xml