feat(17-03): full sitemap generation, settings, hooks and import commands

- generator in Definition::addItemToSet order: 50000 URL cap, lastmod from
  the record or the updates manifest (regular file, 5 MiB cap, fail safe),
  BeforeAddItem (skip) and AddItem (extra XML) festival events, tier or item
  priority, per-alternate expansion of list type children
- priority tiers from golem15.sitemap.priority_tiers, compiled at boot,
  defaults equal to the PHP getPriorityForUrl rules
- frontend_url rewrite of loc, xhtml:link href and the stylesheet href;
  GET /sitemap.xsl serves the PHP stylesheet byte for byte
- golem15_sitemap_settings singleton and Settings model
- sitemap:import (PHP ImportCommand) and sitemap:import-winter with the
  read-only Winter export SQL
- urlto and full goldens generated from PHP; TestSitemapImportSmoke

classes/testdata/urlto.json

@@ -0,0 +1,63 @@
+{
+  "root": "https://api.ex.pl",
+  "urls": [
+    "/",
+    "",
+    null,
+    "/blog/",
+    "/blog",
+    "blog",
+    "/blog/zażółć gęślą",
+    "/en/blog/:slug",
+    "https://x.pl/q/",
+    "http://x.pl",
+    "HTTP://X.pl:443/a",
+    "https://h:8080/a",
+    "https://h:443/a",
+    "http://h:80/",
+    "/a?b=1&c=2",
+    "/a?x[]=1&x[]=2&y",
+    "/a?q=a%26b+c",
+    "/a?",
+    "/a?b=&c",
+    "/a?0=x&1=y",
+    "/a?a=1&a=2",
+    "/a?a[b]=1",
+    "/a#b c",
+    "/a#",
+    "#frag",
+    "//cdn.x/a",
+    "mailto:a@b.pl",
+    "tel:+48 123",
+    "sms:+48123",
+    "/../a/./b/../c",
+    "/a//b",
+    "/a/%20b/%zz",
+    "/a%2Fb",
+    "/ścieżka/ąę?x=ż#ł",
+    "ftp://x.pl/a b",
+    "ftp://x.pl/a",
+    "news:comp.x",
+    "/a:b",
+    "a:1",
+    "/user@host",
+    "https://user:pass@h/x",
+    "  /lead",
+    "/trail  ",
+    "/tab\there",
+    "/new\nline",
+    "/a/b/../../..",
+    "javascript:alert(1)",
+    "https://a&b<c>.pl/x",
+    "https://h/./",
+    "/en",
+    "/en/",
+    "/a?x=%2B",
+    "/a?k=v w",
+    "/a b?x=1#y z",
+    "https://h/a?b=1#c",
+    "/~tilde/_under.dot-dash",
+    "/a'b\"c",
+    "/<x>&y"
+  ]
+}