ListAttr: new attribute type for lists of literals

used in: interface->addresses, rule->in-ports, rule->out-ports

Signed-off-by: Guillermo Ontanon <guillermo@midokura.jp>
Add the sort_by property for collections

Signed-off-by: Guillermo Ontanon <guillermo@midokura.jp>
Fix a typo in chain.rule attr definition

Signed-off-by: Guillermo Ontanon <guillermo@midokura.jp>