* new simple 'invalid reply rate' tracking the number of replies a peer sends that Suck.

(e.g. we can't find the referenced peer or the data they send back is corrupt/expired).
This is like the old invalidReplies, except its a rate that decays.
* if we receive more than 5 invalid replies from a peer in a 1-2 hour period,
stop verifying any subsequent replies, and also stop asking them for keys.
* cleaned up the store validation even further