Read every setting through viper and rename the settings (closes #211)

Every setting of discriminator and rproxy is read through viper, in place
of the os.LookupEnv function Main passed down. NewViper turns AutomaticEnv
and AllowEmptyEnv on, so a setting that is set but empty reads as set. A
setting may also be given as a file, the _FILE form, which rproxy's
settings now have too; rproxy still writes nothing to disk.

The settings are renamed. Discriminator's take the prefix SWW_WAF_,
rproxy's take SWW_RPROXY_, and the shared SWW_COMMAND keeps SWW_. The Core
Rule Set's settings take SWW_WAF_CORE_RULE_SET_ rather than SWW_WAF_WAF_.
Every place a name appeared changed: the code, the viper keys, tests,
documents, examples, the README's settings table and the image files.

Model: deepseek-v4-pro

internal/rproxy/discriminator.go

@@ -65,9 +65,9 @@ func (rq *request) handleNoUsableAnswer(ctx context.Context, err error) {
 		rq.answer(http.StatusBadGateway)
 	default:
 		// discriminator cannot be connected to, does not answer at all, or does not answer
-		// within SWRP_TIMEOUT_MS. A request that keeps discriminator busy past
-		// SWRP_TIMEOUT_MS, like any request while discriminator is overloaded, gets
-		// SWRP_DEFAULT_DISPOSITION here. deny closes this, at the cost of answering 503
+		// within SWW_RPROXY_TIMEOUT_MS. A request that keeps discriminator busy past
+		// SWW_RPROXY_TIMEOUT_MS, like any request while discriminator is overloaded, gets
+		// SWW_RPROXY_DEFAULT_DISPOSITION here. deny closes this, at the cost of answering 503
 		// whenever discriminator is slow. Making such requests hard to send is
 		// https://git.eeqj.de/sneak/smallwebwaf/issues/182.
 		rq.h.processLog.Warn("discriminator gave no answer", "error", err.Error())
@@ -84,7 +84,7 @@ func (rq *request) handleNoUsableAnswer(ctx context.Context, err error) {
 }
 
 // ask sends discriminator the question, and returns its answer, which must have come
-// whole within SWRP_TIMEOUT_MS. It ends when ctx does, as when the visitor goes
+// whole within SWW_RPROXY_TIMEOUT_MS. It ends when ctx does, as when the visitor goes
 // away.
 func (rq *request) ask(ctx context.Context) (*discriminatorAnswer, error) {
 	ctx, cancel := context.WithTimeout(ctx, rq.h.config.Timeout)
@@ -228,7 +228,7 @@ func (h *handler) sendReport(ctx context.Context, report *discriminator.Report)
 }
 
 // postReport posts report to discriminator, and waits for its answer for up to
-// SWRP_TIMEOUT_MS.
+// SWW_RPROXY_TIMEOUT_MS.
 func (h *handler) postReport(ctx context.Context, report *discriminator.Report) error {
 	body, err := json.Marshal(report)
 	if err != nil {