update wallpapers

Change-Id: I632fa28915eba8cfcf993f79e2b9da5c8e7a202f

Conflicts:
	core/res/res/drawable-nodpi/default_wallpaper.jpg
	core/res/res/drawable-sw600dp-nodpi/default_wallpaper.jpg
	core/res/res/drawable-sw720dp-nodpi/default_wallpaper.jpg
	core/res/res/drawable-xhdpi/default_wallpaper.jpg
	core/res/res/drawable-xxhdpi/default_wallpaper.jpg