[Frontend] Fixed CSS issue with Timeline label elements

open #659
CSS for .rep-object-label modified; Added CSS class
to tabular-swimlane-cols-tree.html markup;
Also cleaned up .s-status-pending styles for related
label elements;

platform/features/timeline/res/templates/tabular-swimlane-cols-tree.html

@@ -50,6 +50,7 @@
               ng-style="{ 'margin-left': 15 * ngModel.depth + 'px' }">
             <mct-representation key="'label'"
                                 mct-object="ngModel.domainObject"
+                                class="rep-object-label"
                                 mct-swimlane-drag="ngModel">
             </mct-representation>
         </span>