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
As discussed, that value is a float, so leaving it as day(s).
Moved to attributes as suggested on chat (shame on me): b6e9e9a
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