[Mobile] Sanding of mobile styles continues, in progress

open #74
CSS and markup changes for split pane holders;
drop shadow added to tree area;
Tree item cleanups;
This or earlier commit broke treeview nav action;
TO-DO: fix treeview nav action to hide menu;

platform/commonUI/general/res/sass/_constants.scss

@@ -110,6 +110,7 @@ $ueBrowseGridItemBottomBarH: 30px;
 $itemPadLR: 5px;
 // Tree
 $treeVCW: 10px;
+$treeTypeIconH: 16px;
 $treeTypeIconW: 20px;
 $treeContextTriggerW: 20px;
 $colorItemTreeIcon: $colorKey;