fix(autocomplete): md-not-found template is not styled properly

- also fix some styling issues with the docs-menu sidenav
  caused by CSS specificity changes

Fixes #11852

Author: Splaktar

docs/app/css/style.css

@@ -155,13 +155,13 @@ ul {
   margin: 0;
   padding: 0;
 }
-ul:not(.md-autocomplete-suggestions) li:not(.md-nav-item) {
+main ul:not(.md-autocomplete-suggestions) li:not(.md-nav-item) {
   margin-left: 16px;
   padding: 0;
   margin-top: 3px;
   list-style-position: inside;
 }
-ul:not(.md-autocomplete-suggestions) li:not(.md-nav-item):first-child {
+main ul:not(.md-autocomplete-suggestions) li:not(.md-nav-item):first-child {
   margin-top: 0;
 }
 /************

src/components/autocomplete/js/autocompleteDirective.js

@@ -429,7 +429,7 @@ function MdAutocomplete ($$mdSvgRegistry) {
         var templateTag = element.find('md-not-found').detach(),
             template = templateTag.length ? templateTag.html() : '';
         return template
-            ? '<li ng-if="$mdAutocompleteCtrl.notFoundVisible()"\
+            ? '<li ng-if="$mdAutocompleteCtrl.notFoundVisible()" class="md-autocomplete-suggestion"\
                          md-autocomplete-parent-scope>' + template + '</li>'
             : '';
       }