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/grants.html

@@ -1,7 +1,3 @@
-{{ template "_base.html" . }}
-{{ define "title" }}{{ .Instance.Slug }} - Grants{{ end }}
-
-{{ define "content" }}
 {{ $csrf := .CSRF }}
 {{ $slug := .Instance.Slug }}
 <div class="pure-u-1-1">
@@ -123,5 +119,4 @@
     {{ range $unused, $drupal := .Drupals }}
         <option value="{{ $drupal }}">
     {{ end }}
-</datalist>
-{{ end }}
+</datalist>