build(aio): remove formatting and styles from dgeni templates

Much of the formatting was hardcoded and copied from the old anguar.io
jade files. This gives us a clean start.

Also, more use has been made of include files to make the templates
easier to understand and manage.

docs/templates/includes/_annotations.html

@@ -0,0 +1,13 @@
+{%- if doc.decorators.length %}
+<section class="annotations">
+  <h2>Annotations</h2>
+  <div class="annotation">
+    {%- for decorator in doc.decorators %}
+      <pre class="prettyprint no-bg">
+        <code>@{$ decorator.name $}{$ params.paramList(decorator.arguments) | indent(10, false) $}</code>
+      </pre>
+      {%- if not decorator.notYetDocumented %}{$ decorator.description | marked $}{% endif %}
+    {% endfor %}
+  </div>
+</section>
+{% endif %}