Refactor html templates

This commit entirely refactors the use of html templates. Instead of
inheriting from a shared template, we insert the results into a base
template.

internal/dis/component/server/admin/html/index.html

@@ -1,7 +1,3 @@
-{{ template "_base.html" . }}
-{{ define "title" }}Admin{{ end }}
-
-{{ define "content" }}
 <div class="pure-u-1-1">
     <h2 id="overview">Distillery Configuration</h2>
 </div>
@@ -256,5 +252,4 @@
         </p>
     </div>
 </div>
-{{end}}
-{{ end }}
+{{end}}