dpkg: support pkg-map in bin/install-packages

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
Merge "dpkg: support pkg-map in bin/install-packages"