[Frontend] Further cleanups to form elements

#700
#689
#740
Removed _selects.scss and moved classes
into _controls.scss;
Reorg'd _controls;
Moved classes into _elems.scss;
Added and fixed cssclass defs in multiple
bundle.js files to allow better field widths
in overlay dialogs;
Fixed overlay custom scrollbar colors;
Fixed alignment of required glyphs in forms;

platform/features/layout/bundle.js

@@ -278,12 +278,12 @@ define([
                                 {
                                     "name": "Horizontal grid (px)",
                                     "control": "textfield",
-                                    "cssclass": "l-small l-numeric"
+                                    "cssclass": "l-input-sm l-numeric"
                                 },
                                 {
                                     "name": "Vertical grid (px)",
                                     "control": "textfield",
-                                    "cssclass": "l-small l-numeric"
+                                    "cssclass": "l-input-sm l-numeric"
                                 }
                             ],
                             "key": "layoutGrid",