Restored html_default_sidebars setting; added JS TOC to modules sidebar

Using JavaScript to generate a local table of contents for the modules
is less than ideal but this isn't easily accomplished with autosummary
(see 87c1000) and we badly need this.

doc/_templates/modules-sidebar.html

@@ -0,0 +1,30 @@
+<div id="module-funcs"></div>
+
+<script>
+    jQuery.fn.local_toc = function(tgt_sel) {
+        var tgt = jQuery(tgt_sel);
+
+        tgt.append('<h4>Table of Contents</h4>');
+
+        jQuery('dt .headerlink').each(function(idx, elem) {
+
+            var i = [
+                '<li><a href="', elem.href, '">',
+                last(elem.href.split('.')),
+                '</a></li>']
+            .join('');
+
+            tgt.append(i);
+        });
+
+        function last(list) {
+            return list[list.length - 1];
+        }
+    };
+</script>
+
+<script>
+;(function($) {
+    $.fn.local_toc('#module-funcs');
+})(jQuery);
+</script>

doc/conf.py

@@ -143,8 +143,15 @@ def __getattr__(self, name):
     '404': '404.html',
 }
 
+html_default_sidebars = [
+    'localtoc.html',
+    'relations.html',
+    'sourcelink.html',
+    'searchbox.html',
+]
 html_sidebars = {
-    '**': [
+    'ref/**/all/salt.*': [
+        'modules-sidebar.html',
         'localtoc.html',
         'relations.html',
         'sourcelink.html',