CM11 Themes: Clear wallpaper mixnmatch entry on external change

If a wallpaper is applied from a theme and the wallpaper is changed
from an external source, the theme is still shown to have its
wallpaper applied.  This patch will clear this value out when a
wallpaper change is detected that is not from the ThemeService.

Change-Id: I3d32bb3c0ac96db3f940989bc7ad4eda5e4a71f7
persist the changed position values in updateWallpaperOffsetLocked, even with a null mWallpaperTarget

Change-Id: I175773f6e0b3f91c1d983857028a89b959e4e9f2
Notify callbacks on "any" wallpaper change

Callbacks are not notified when the wallpaper is changed to
a live wallpaper.  This patch notifies callbacks of the change
regardless of the type of wallpaper be set.

Change-Id: Icbb7b825cd7e7096c90c5498b6fee0bc61a3de3b
Automatic translation import

Change-Id: I0b81b54da81b39d2158eeb70123b96a252f14156