Make yaml settings more generic

This PR greatly simplifies dcr configuration file.
It replaces the well established $ for what most people expect from it and use % instead:

eg: ( assumed SERVER='192.168.1.1' environment variable )
Both  "SERVER=$SERVER"  and  "%SERVER"  are expanded as  "SERVER=192.168.1.1"

Also $ expansion is used in settings.yml to make them easier to organize