[Frontend] New symbols font and CSS adjustments

WTD-980
WTD-396
Changed glyph for stacked plots;
Normalized button line-heights and size of required symbol;
Updated symbol art in symbols font;
Restored mistakenly removed "menu" gesture to grid-item;

platform/features/plot/src/modes/PlotModeOptions.js

@@ -29,7 +29,7 @@ define(
         var STACKED = {
                 key: "stacked",
                 name: "Stacked",
-                glyph: "8",
+                glyph: "m",
                 factory: PlotStackMode
             },
             OVERLAID = {