Revert "Purity dark UI mode toggle"

This reverts commit ca63acccb3b6a288e47e7fce826890dd4953bdce.

Conflicts:
	core/res/res/drawable-inverted-hdpi/cab_background_top_holo_dark.9.png
	core/res/res/drawable-inverted-hdpi/ic_lockscreen_gtalk_activated.png
	core/res/res/drawable-inverted-mdpi/ic_lockscreen_gtalk_activated.png
	core/res/res/drawable-inverted-xhdpi/ic_lockscreen_gtalk_activated.png