[Frontend] Manual re-do of collapse/expand panes

open #90
Fixed broken mobile styles;
Removed commented out scss;

platform/commonUI/general/res/sass/mobile/_layout.scss

@@ -80,11 +80,7 @@
 
         // Sets the left tree menu when the tree is shown.
         .pane.left.treeview {
-            //@include trans-prop-nice(opacity, .4s);
             @include background-image(linear-gradient(90deg, rgba(black, 0) 98%, rgba(black, 0.3) 100%));
-            //opacity: 1;
-            //display: block !important;
-            //width: auto !important; // CH CO
             right: auto !important;
             width: $proporMenuWithView !important;
         }
@@ -95,11 +91,12 @@
     }
 
     .toggle-tree {
+        color: $colorKey !important;
         font-size: 110%;
         position: absolute;
         top: $bodyMargin + 2;
         left: $bodyMargin;
-        &:before {
+        &:after {
             content:'m' !important;
         }
     }