Rename the program to sww and its deciding daemon to discriminator (closes #218)

The program is now sww, built from cmd/sww, with two modes: sww rproxy and
sww discriminator. servewaf becomes discriminator everywhere it names that
daemon: the package (internal/discriminator), its types, functions, files, the
discriminator_line log field, and its docs and tests.

smallwebwaf is left only where sneak's directive allows it: the documents'
product name, the git.eeqj.de/sneak/smallwebwaf URLs, and the Go module path
sneak.berlin/go/smallwebwaf. Everywhere else a name containing it takes the sww
form: the package (internal/sww), metric names (sww_*), the X-Sww-* headers,
the /_sww/ admin endpoints, the OS user, and the state and rules directories.
The SWWAF_ environment variables take the SWW_ form.

No logic changes. make check passes.

Model: deepseek-v4-pro

internal/lookup/lookup.go

@@ -1,6 +1,6 @@
 // Package lookup looks up each client's AS number and country, through
 // the GeoJS web service or in the lookup database, the IPinfo Lite file
-// SWWAF_LOOKUP_DB_PATH names. GeoJS's answers are kept in memory, for at
+// SWW_LOOKUP_DB_PATH names. GeoJS's answers are kept in memory, for at
 // most 100,000 clients and for 7 days each, and are written to
 // lookups.json and read from it by the state package.
 package lookup
@@ -66,7 +66,7 @@ type Params struct {
 	URL string
 	// Timeout is how long a request waits for its client's first answer,
 	// and how long a request to GeoJS may take before it is abandoned
-	// (SWWAF_LOOKUP_TIMEOUT).
+	// (SWW_LOOKUP_TIMEOUT).
 	Timeout time.Duration
 	// Wait is true when a setting needs each request's answer before the
 	// request goes on. Otherwise no request waits for one.