Rename app id from occweb to extended_occweb, prep for App Store

Nextcloud's app id "occweb" is effectively unavailable for a new store
listing: the original Adphi/occweb still owns that App Store slot
(stale, v0.2.3), and el-choco/occweb_v2 has since published a
same-lineage rewrite under its own id. Rather than fight over the
"occweb" name, publish this fork under its own id, matching the
<name> this app has always had: "Extended OCC Web".

Renames every place the literal app id is used: info.xml <id> and the
auto-generated navigation <route>, script()/style() registrations in
templates/index.php, the TemplateResponse app name in
OccController::index(), the /apps/... base URL in js/index.js, and the
'app' log context tag in DbController.php. The GitHub repo name and
its <website>/<bugs>/<repository>/<screenshot> links are unaffected -
those identify the repo, not the Nextcloud app.

Docs (README, INSTALL-AIO.md, install.sh) updated to clone into and
reference an "extended_occweb" directory, since Nextcloud requires the
app folder name to match its id - a plain `git clone` of this repo no
longer produces a correctly-named install directory on its own.

Version bump to 0.4.0 given the scope (breaking change for anyone who
already deployed under the old "occweb" id - requires disable+remove
of the old app and a fresh enable under the new id, not an in-place
upgrade).

lib/Controller/OccController.php

@@ -70,7 +70,7 @@ class OccController extends Controller
   public function index()
   {
     if ($err = $this->requireAdmin()) return $err;
-    return new TemplateResponse('occweb', 'index');
+    return new TemplateResponse('extended_occweb', 'index');
   }
 
   /**