[Frontend] Markup and CSS for loading tree items

#445
New wait-spinner constants;
Markup fixed in wait-node.html;
Styles for .loading when applied to
.tree-item.wait-node;
Changed from percent-of-parent-
width sizing of spinner to fixed size;

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

@@ -98,6 +98,9 @@ $bubbleMaxW: 300px;
 $reqSymbolW: 15px;
 $reqSymbolM: $interiorMargin * 2;
 $reqSymbolFontSize: 0.7em;
+// Wait Spinner Defaults
+$waitSpinnerD: 32px;
+$waitSpinnerBorderW: 5px;
 
 /************************** CONTROLS */
 $controlDisabledOpacity: 0.3;