Move HTML generation back to JavaScript.

- Functionality maintained
- File operations removed from server
- Browsers should again be able to cache the tutorial

WebHostLib/templates/tutorial.html

@@ -3,11 +3,14 @@
 {% block head %}
     <title>Setup Tutorial</title>
     <link rel="stylesheet" type="text/css" href="{{ static_autoversion("styles/tutorial.css") }}" />
+    <script src="https://cdnjs.cloudflare.com/ajax/libs/showdown/1.9.1/showdown.min.js"
+            integrity="sha512-L03kznCrNOfVxOUovR6ESfCz9Gfny7gihUX/huVbQB9zjODtYpxaVtIaAkpetoiyV2eqWbvxMH9fiSv5enX7bw=="
+            crossorigin="anonymous"></script>
     <script type="application/ecmascript" src="{{ static_autoversion("assets/tutorial.js") }}"></script>
 {% endblock %}
 
 {% block body %}
-    <div id="tutorial-wrapper" class="main-content">
-        {{ tutorial|safe }}
+    <div id="tutorial-wrapper" class="main-content" data-language="{{ lang }}">
+        <!-- Content generated by JavaScript -->
     </div>
 {%  endblock %}