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/_constructor.html

@@ -0,0 +1,16 @@
+{%- if doc.constructorDoc and not doc.constructorDoc.internal %}
+<section class="constructor">
+  <h2>Constructor</h2>
+  <div class="description">
+    <a name="constructor" class="anchor-offset"></a>
+    <pre class="prettyprint no-bg" ng-class="{ 'anchor-focused': appCtrl.isApiDocMemberFocused('{$ doc.constructorDoc.name $}') }">
+      <code>
+        {$ doc.constructorDoc.name $}{$ params.paramList(doc.constructorDoc.parameters) | indent(8, false) | trim $}
+      </code>
+    </pre>
+    {%- if not doc.constructorDoc.notYetDocumented %}
+    {$ doc.constructorDoc.description | replace('### Example', '') | replace('## Example', '') | replace('# Example', '') | trimBlankLines | marked $}
+    {% endif %}
+  </div>
+</section>
+{% endif %}