feat!: move every layout to demo folder

- source/screens is now free for user files
- rename demo templates to their equivalent sources
- add demo maintenance template
- demo templates use html base element

source/screens/demo/introduction.njk

@@ -0,0 +1,53 @@
+<!-- introduction.page -->
+{% set pageBase = "../" %}
+{% set pageId = "intro" %}
+
+{% extends "demo/_main.njk" %}
+
+{% block title %}Einführung{% endblock %}
+{% block head %}
+  {{ super() }}
+{% endblock %}
+
+{% block main %}
+  {% include "hippie/partials/_body_nav.njk" %}
+
+  <section class="sec_main_center">
+    <header>
+      <hgroup>
+        <h1>Introduction to HIPPIE</h1>
+        <p>Hippie interweaves preeminent personal interface elements.</p>
+      </hgroup>
+    </header>
+    <article>
+      <p>&hellip;</p>
+    </article>
+  </section>
+{% endblock %}
+
+{% block script %}
+  {{ super() }}
+  {# <script src="{{ pageBase }}js/{{hippie.jsFile}}.min.js" type="text/javascript"></script> #}
+  <!-- build:js js/main.concat.min.js -->
+  <script src="{{ pageBase }}js/variables.js"></script>
+  <script src="{{ pageBase }}js/functions.js"></script>
+  <script src="{{ pageBase }}js/global.js"></script>
+  <script>
+    assetsLoaded = true;
+    logPerf('Assets loaded.', assetsLoaded);
+    // Page specific
+    // ------------------------------------------------------------------------------
+    // Create instance of object made by contructor function
+    var scrollUi = new HippieScroll($('.js_scrolltop'), $('.js_scrolldown'));
+    var helpUi = new HippieMeta($('.js_showmeta'), $('.js_pop'));
+
+    $(document).ready(function () {
+      logPerf('JQ document ready event fired.');
+    });
+
+    $(document).scroll(function () {
+      scrollUi.check();
+    });
+    logPerf('Application ready... not.');
+  </script>
+{% endblock %}