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/rulefiles.go

@@ -1,7 +1,7 @@
 package waf
 
 // The heuristic rule_files. It reads the rules of the rule files, which
-// SWW_WAF_RULES_DIR and SWW_WAF_RULES_ENABLED name.
+// SWW_WAF_RULE_FILES_DIR and SWW_WAF_RULE_FILES_ENABLED name.
 
 import (
 	"context"