[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/_constants.scss

@@ -47,6 +47,7 @@ $ueBrowseRightPaneInspectW: 10%;
 $ueEditLeftPaneW: 75%;
 $treeSearchInputBarH: 25px;
 $ueTimeControlH: (33px, 20px, 20px);
+$ueCollapsedEdgeMargin: 15px;
 // Overlay
 $ovrTopBarH: 60px;
 $ovrFooterH: 30px;