Caches of outside APIs live in /var/cache/sww (closes #314)

The answers of GeoJS, the lists fetched by URL, the DNS blocklists,
AbuseIPDB and routewatch each go in a cache file in SWW_CACHE_DIR
(default /var/cache/sww): lookups.json, lists.json, dnsbl.json,
abuseipdb-scores.json and routewatch.json. reputation.json is gone. The
AbuseIPDB checks spent today are a count, not a cache, and stay in
SWW_STATE_DIR as abuseipdb-checks-spent.json.

A cache file never stops the start: one that does not parse is set
aside as an edit is, one that cannot be read is written over, and its
cache starts empty. An unwritable SWW_CACHE_DIR stops the start, as an
unwritable SWW_STATE_DIR does. Each directory is watched on its own.
The run script makes the cache directory and gives it to sww.

Model: opus-5-5

script/run

@@ -6,8 +6,9 @@
 # waf listens on port 8090 unless SWW_LISTEN_ADDR says otherwise, and
 # rproxy asks it there unless SWRP_WAF_BACKEND says otherwise. Unless
 # SWW_STATE_DIR is set, the state files go in bin/state, beside the binary,
-# and unless SWW_RULES_DIR is set, the rule files are those of share/rules.d,
-# which the image ships.
+# and unless SWW_CACHE_DIR is set, the cache files go in bin/cache. Unless
+# SWW_RULES_DIR is set, the rule files are those of share/rules.d, which the
+# image ships.
 set -eu
 
 SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd -P)"
@@ -31,6 +32,11 @@ main() {
         export SWW_STATE_DIR
         mkdir -p "$SWW_STATE_DIR"
     fi
+    if [ -z "${SWW_CACHE_DIR+set}" ]; then
+        SWW_CACHE_DIR="$ROOT/bin/cache"
+        export SWW_CACHE_DIR
+        mkdir -p "$SWW_CACHE_DIR"
+    fi
     if [ -z "${SWW_RULES_DIR+set}" ]; then
         SWW_RULES_DIR="$ROOT/share/rules.d"
         export SWW_RULES_DIR