Rename the settings whose names do not say what they control (closes #234)

Applies the setting renames of the naming audit under the SWW_WAF_ and
SWW_RPROXY_ prefixes, with sneak's names for the IP reputation cache
time and the two time limits, which now take milliseconds. The rproxy
log field default_disposition becomes waf_backend_no_answer, and
config.Config and config.FromEnvironment become config.WAF and
config.WAFFromEnvironment. Go fields, test names and prose follow. No
aliases; nothing reads the old names.

Model: opus-5-5

internal/waf/heuristics.go

@@ -7,7 +7,7 @@ import (
 
 // To add a heuristic, write one file with a type that implements heuristic,
 // and add one line for it to one of the lists below. Its settings go in
-// config.Config, and the comment at the top of its file names them.
+// config.WAF, and the comment at the top of its file names them.
 
 // heuristic is one of the checks that decide what waf does with a
 // request.