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/function.template.html

@@ -1,31 +1,6 @@
-{% import "lib/githubLinks.html" as github -%}
 {% import "lib/paramList.html" as params -%}
-{% extends 'layout/base.template.html' -%}
+{% extends 'layout/api-base.template.html' -%}
 
-{% block body %}
-
-
-{% include "layout/_what-it-does.html" %}
-
-{% include "layout/_security-notes.html" %}
-
-{% include "layout/_deprecated-notes.html" %}
-
-{% include "layout/_how-to-use.html" %}
-
-<div layout="row" layout-xs="column" class="row-margin ng-cloak">
-  <div flex="20" flex-xs="100">
-    <h2 class="h2-api-docs">Class Export</h2>
-  </div>
-  <div class="code-links" flex="80" flex-xs="100">
-    <pre class="prettyprint no-bg">
-      <code>
-        export {$ doc.name $}{$ params.paramList(doc.parameters) | indent(8, true) | trim $}{$ params.returnType(doc.returnType) $}
-      </code>
-    </pre>
-    {%- if not doc.notYetDocumented %}{$ doc.description | trimBlankLines | marked $}{% endif %}
-
-<p class="location-badge">
-  exported from {@link {$ doc.moduleDoc.id $} {$doc.moduleDoc.id $} } defined in {$ github.githubViewLink(doc, versionInfo) $}
-</p>
+{% block main %}
+  {% include "includes/_description.html" %}
 {% endblock %}