[Frontend] Tweaks to splitter

Fixes #913
- IN PROGRESS: working on making
smaller splitter in Timelines

platform/commonUI/themes/snow/res/sass/_constants.scss

@@ -183,8 +183,9 @@ $scrollbarThumbColorOverlay: darken($colorOvrBg, 50%);
 $scrollbarThumbColorOverlayHov: $scrollbarThumbColorHov;
 
 // Splitter
-$splitterD: 24px;
+$splitterD: 24px; // splitterD and $splitterHandleD should both be odd, or even
 $splitterHandleD: 2px;
+$splitterDSm: 16px; // Smaller splitter, used inside elements like a Timeline view
 $colorSplitterBg: pullForward($colorBodyBg, 10%);
 $splitterShdw: none;
 $splitterEndCr: none;