[Frontend] Significant change to look and behavior of mini-tabs

open #90
IN-PROGRESS
mini-tab location in markup in browse.html changed;
Single menu icon for collapsed treeview;
Close 'x' boxes instead of arrow icons;
TO-DO: verify mobile is Ok;

platform/commonUI/general/res/sass/helpers/_splitter.scss

@@ -44,7 +44,7 @@
     }
     &:not(:active) {
         &:after {
-            @include trans-prop-nice(background-color, 250ms);
+            @include trans-prop-nice(background-color, 150ms);
         }
     }
     &:active {
@@ -55,7 +55,10 @@
 
     @if $colorSplitterHover != 'none' {
         &:hover {
-            background: $colorSplitterHover;
+            &:after {
+                @include trans-prop-nice(background-color, 150ms);
+                background-color: $colorSplitterHover;
+            }
         }
     }
 }