Implemented the "ref" namespace to get configuration tree references. BUGS: - Tests should be done more thoroughly and extensively - Interaction of tree references and variable substitution should be tested more properly - Documentation is missing yet

{"tmpdir": "{{_tmpdir}}\\3",
 "db": {
     "user": {
	 "name": "the_database_user_2",
	 "__doc2": "comment",
	 "pwd": "the-database-password-2"
     },
     "locinfo": {
	 "ro": {
	     "hostname": "3rd-host"
	 }
     }
 }
}