LauncherModel : Ensure checkItemPlacement key casting

Ensure the key is casted correctly.

Change-Id: Id0ac5ab878d1d059c138ae294a3eff63bf0d858b
Launcher3: add lockscreen wallpaper picker

Change-Id: Ic4f2589924a3c61b676db907f08108286dc45c29
Signed-off-by: Roman Birg <roman@cyngn.com>

Conflicts:
	res/values/cm_strings.xml