Metering: let rule conditions match on traversed devices

Change-Id: I3b549b4cb324571b918df358544386d443dceb02
Signed-off-by: Guillermo Ontanon <guillermo@midokura.jp>
mm-stat: rewrite

Change-Id: Ie49769462c120e719262d4cb731648cb010bac7d
Signed-off-by: Guillermo Ontanon <guillermo@midokura.jp>
wip: metering

Change-Id: I9064545e7085e5b29d8326bca1e02eccea45594e
Signed-off-by: Guillermo Ontanon <guillermo@midokura.jp>