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/_title.html

@@ -0,0 +1,6 @@
+<!-- PAGE HERO -->
+<header>
+  <h1>{$ doc.name $}</h1>
+  <h2>{$ doc.docType $}</h2>
+  <span class="version">{$ angular.version $}</span>
+</header>