Crop wallpaper and lockscreen images before saving them

Images were saved as-is and could cause large heap usage when
Wallpaper loads them later. This patch crop the images to fit the
screen size before saving them (as wallappper cropper activity does)

Change-Id: I08c04d9d14a65355c4417f0414d7a6ac538b3ea0
(cherry picked from commit d604ab35afea00f0d06a9235cf3fe5cc6edf441b)