Threat control LWRP

Cf. first commit and README changes:

Add a threat_control LWRP, allowing to whitelist/blacklist IPs on CloudFlare
* Stores last action in a node attribute cache, CF API is only called once per day, or if status changes
* IP attribute defaults to current's node IP address
That's really disputable, and I don't remember any readability guidelines surrounding De Morgan's laws. :-)
I'll go for `!A && !B` though, it does look easier to read here.
4729b30