[Fronted] Significant refactoring of btn classes

WTD-839
Refactoring in advance of style mods to switcher when in frame;
Moved btn styles from _controls.scss to _buttons.scss;
Markup cleaned up with css classing simplified;

platform/commonUI/browse/res/templates/browse-object.html

@@ -21,14 +21,12 @@
 -->
 <span>
     <div class="object-browse-bar bar abs">
-
         <div class="items-select left abs">
             <mct-representation key="'object-header'" mct-object="domainObject">
             </mct-representation>
         </div>
 
         <div class="view-controls sort-controls btn-bar right abs">
-
             <mct-representation key="'action-group'"
                                 mct-object="domainObject"
                                 parameters="{ category: 'view-control' }">
@@ -39,7 +37,6 @@
                                 ng-model="representation">
             </mct-representation>
         </div>
-
     </div>
 
     <div class='object-holder abs vscroll'>