improve superset list view page layout

- less header spaces and stacks
- move pagination down to bottom
- apply material design style to 'add' action button
- will apply to all superset list view, like slices list, security tab lists etc.

superset/assets/stylesheets/superset.css

@@ -275,6 +275,9 @@ div.widget .slice_container {
 .list-container .pagination-container .pagination {
     margin: 0 15px;
 }
+.list-container .pagination-container strong {
+    margin-right: 5px;
+}
 
 .list-container .list-add-action {
     position: absolute;
@@ -288,7 +291,7 @@ div.widget .slice_container {
 }
 
 .list-container .filter-action {
-    margin: 0 15px;
+    margin: 0 10px;
     padding-bottom: 15px;
 }
 

superset/templates/appbuilder/general/widgets/search.html

@@ -37,9 +37,7 @@
         }
     }
 
-    $('.list-search-container').on('hidden.bs.dropdown', function () {
-        checkSearchButton();
-    });
+    $('.list-search-container').on('hidden.bs.dropdown', checkSearchButton());
     $(document).ready(function() {
         checkSearchButton();
     });