Say which bytes the byte limits count, and what passing one does (closes #203)

The byte limits and the byte anomaly thresholds count body bytes, as
SWW_BYTES_COUNT chooses them, once a response has ended; the request
that takes a client past a limit is passed on whole, and the client is
banned. README.md, SPEC.md and docs/settings.md now say so where they
said "bytes a client's requests may carry". Also made plain: a request
past a rate limit is refused and bans the client; SWRP_MAX_REQUEST_TIME_MS
is two consecutive limits; SWW_LOOKUP_SOURCE's three values; and the
claim that discriminator always answers within SWRP_TIMEOUT_MS, which
the spec itself contradicts.

Model: fable-5-1

docs/state-files.md

@@ -61,7 +61,7 @@ since it was first seen:
 - the first and last time seen;
 - the AS number, AS name and country last looked up, and when;
 - total requests, and how many were forwarded and how many refused;
-- bytes in each direction;
+- body bytes of its requests, and of the responses it was sent;
 - responses by status class;
 - offences by kind: `limit`, `attack`, `rule_blocked` and `waf_blocked`. A file
   may also hold `token_refused`, which is kept, and which nothing adds to.