修改所有Dropdown-Menu样式，取消上下的padding导致的间隙

Bootstrap.Admin/Content/css/admin.css

@@ -499,17 +499,14 @@ input[type="datetime"] {
                     cursor: pointer;
                 }
 
-.btn-select {
+.dropdown-menu {
+    padding: 0;
 }
 
-    .btn-select .dropdown-menu {
-        padding: 0;
-    }
-
-        .btn-select .dropdown-menu li a {
+    .dropdown-menu li a {
         padding: 6px 20px;
     }
 
-        .btn-select .dropdown-menu .divider {
+    .dropdown-menu .divider {
         margin: 0;
     }