Deprecate map-packages, replaced by pkg-map

This patch writes a warning out to stderr to notify element authors
that may be using map-packages to migrate to pkg-map.  This patch
also prints out a warning during image-create that lists the specific
elements that are not using pkg-map.

Change-Id: I7e2a7611dd5650815736ce998aa94a7833193d06
Merge "Deprecate map-packages, replaced by pkg-map"