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

open #90
Animation, styles, hide-show added panes and splitters;
Finessed spacing;
trans-prop* mixins normalized and added delay arg;

platform/commonUI/general/res/sass/controls/_buttons.scss

@@ -109,8 +109,8 @@ $pad: $interiorMargin * $baseRatio;
         //@include test(green);
         $iconD: 12px;
         $arwD: 7px;
-        $arwOffsetX: 1px;
-        $arwAnimOffsetX: 3px;
+        $arwOffsetX: 0px;
+        $arwAnimOffsetX: 2px;
         $arwToLeftAnimX: -1 * $arwAnimOffsetX;
         $arwToRightAnimX: $arwAnimOffsetX;
         $arwToLeftX: ($arwOffsetX + $arwD) * -1;