[Feature Request] pcn-iptables support speed limit moduel

[Polaris0112]

Is your feature request related to a problem? Please describe.

1. Could pcn-iptables support speed limit for internal ip address, like iptables hashlimit moduel
2. Could pcn-iptables block by the string match, and block like "p2p" or "bt" packet filter.

Describe the solution you'd like

1. iptables speed limit, iptables mangle mark and use tc to limit
2. iptables string model can match some keywords to drop packet