Updates the dpkg element's bin/install-packages script
so that if supports using pkg-map for package mapping.
To make use of the new change simply add the -m <element name>
to allow install-packages to know which element namespace to use
when installing packages.
Use of the new -m option is off by default.
As part of this change we also updated install-packages
to use getopt for in script argument parsing.
Change-Id: Idfc40f2d75828a0f09d227f0332ccef8f0183efc
9340ea309b