(CFACT-64) Add structured operating system fact

This commit adds a new 'os' structured fact, which returns a map
including keys for each of the operatingsystem-releated facts. The
fact also includes LSB keys in Linux systems where LSB is available.
(CFACT-97) Resolve operatingsystemmajrelease in Ubuntu

This commit adds Ubuntu to the map of platforms which
are suitable to resolve the operatingsystemmajrelease fact,
and adds the necessary logic to do so.