Allow the "when:" statements to be a list of values, which are
effectively anded together to filter the package install.
Change-Id: Ia6f10741fa6be24b11d6991c8a6b6e07951ff68d
Provide a "when" option that provides for not installing packages
based on a = or != match on an environment variable.
Unit tests are added.
Change-Id: Ifa824dccaff69fd447f45d54cb4a3083bcabdd86