Update base element to make use of pkg-map

With this change package name to distro mappings used
within the base element are now stored in the top
level pkg-map file.

Additionally, all bin/install-packages commands are updated
to use the -m option so that the base element pkg-map
namespace is used by default.

Change-Id: I3bdbf987c8525f9ef67ca0c263651d6613f29ef0
Merge "Update base element to make use of pkg-map"