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

Updates the yum element's bin/install-packages script
so that if supports using pkg-map instead of map-packages
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: I19240e74b69859f7faf9cd80440633234a677d63
Merge "Yum: support pkg-map in bin/install-packages"