Added option to switch themes.

Added standalone pages for:
 - Exhibitions
 - Events
 - Institutions
 - Collections
Added option to limit display to only a given set of institutions.

collection.php

@@ -0,0 +1,71 @@
+<?PHP
+/**
+ * This file displays object detail pages as fetched from museum-digital.
+ *
+ * @author Joshua Ramon Enslin <joshua@jrenslin.de>
+ */
+
+// Include functions and settings.
+
+require_once __DIR__ . "/inc/functions.php";
+
+// Check validity of request.
+
+if (!isset($_GET['id']) or !is_numeric($_GET['id'])) {
+    echo printErrorPage("Collection does not exist.");
+    return;
+}
+
+// Ensure working environment for frontend.
+
+ensureEnvironment();
+$pages = loadPublicPages();           // Load overview of pages.
+
+$contents = json_decode(queryCachePage($settings['mdVersion'] . "?t=sammlung&gesusa=" . urlencode($_GET['id']) . "&output=json", "institution", $settings), true);
+
+if (!$contents || (isset($contents[0]) and $contents[0] == "There is no collection with this ID yet.")) {
+    echo printErrorPage("Temporarily unavailable.");
+    return;
+}
+
+if ($settings['limitToInstitutions'] != [] and !in_array($contents['collection_id'], $settings['limitToInstitutions'])) {
+    echo printErrorPage("This collection does not belong to an enabled institution.");
+    return;
+}
+
+/*
+ * Output
+ */
+$addToHead = '
+     <link rel="canonical" href="' . $settings['mdVersion'] . 'index.php?t=sammlung&gesusa=' . $contents['collection_id'] . '" />';
+
+echo printPublicHead($settings, $_GET['id'], $settings['pageTitle'] . " - " . $contents['collection_name'], $settings['logo'], $addToHead);
+echo printPublicHeader($settings['pageTitle']);
+echo printStaticPagePart("banner", "header"); // Print aside (if need be)
+
+echo generatePublicNav($pages);
+
+echo '
+<div id="mainWrapper">
+';
+
+// Print main content
+echo '
+    <main>';
+
+echo drawCollectionDetails($contents, $settings);
+
+echo '
+    </main>
+';
+
+echo printStaticPagePart("aside", "aside"); // Print aside (if need be)
+
+echo '
+</div>';
+
+echo printStaticPagePart("footer", "footer"); // Print footer (if need be)
+
+echo printPublicEnd();
+
+?>