Add wallpaper pickers to seperate package [1/2]

Currently wallpaper pickers were part of the various launchers
and we were relying on Trebuchet's to add code for including
wallpapers from themes.  If Trebuchet is removed then this
functionality is lost.  This package is already included in all
builds so making the picker available here removes the dependency
on a specific launcher.

Trebuchet still contains a picker which should probably be removed
and make use of this package instead.

Change-Id: Ie42ae0e01f951a8293d13d6c8a73fde0dea6682b

Conflicts:
	packages/WallpaperCropper/AndroidManifest.xml
	packages/WallpaperCropper/src/com/android/wallpapercropper/WallpaperCropActivity.java
WallpaperCropper: do not display null bitmaps

It is possible that themes can include a corrupted bitmap,
and the lockscreen will try and display a NULL image resulting in an
empty thumbnail and applying it will cause the app to crash.

Change-Id: Ie0770486a9d58050a5f296a219d844a39937421e
Signed-off-by: Roman Birg <roman@cyngn.com>
WallpaperPicker: Destroy cropview to avoid leaks

If the cropview's TiledImageRenderer is rendering threads, the activity
context gets leaked. Avoid that by invoking its destroy in onDestroy() of activity.

Change-Id: I0804c903d14d3f3d13529f0fe90d12784d97e93f
Fix compilacion

Change-Id: Ic1d349616d2aec844cce8723bb1f3cec56abbfe9