[Frontend] Add grab affordance styling on hover

Fixes nasa#1415
WIP

Author: charlesh88

platform/features/conductor/core/res/sass/_time-conductor-base.scss

@@ -346,7 +346,28 @@
             content: $i;
         }
         .l-axis-holder {
+            $grabTicksH: 8px;
+            $grabTicksXSpace: 3px;
+            $grabTicksYOffset: (($r1H - $grabTicksH) / 2) - 2px;
             @include cursorGrab();
+            &:hover {
+                $c0: rgba($colorBodyFg, 0.05);
+                $c2: transparent; // Bg
+                @include background-image(linear-gradient(
+                    $c0 70%, $c2 100%
+                ));
+                svg {
+                    $c1: rgba($colorBodyFg, 0.15); // Line
+                    $angle: 90deg;
+                    @include background-image(linear-gradient($angle,
+                        $c1 1px, $c2 1px,
+                        $c2 100%
+                    ));
+                    background-position: center $grabTicksYOffset;
+                    background-repeat: repeat-x;
+                    background-size: $grabTicksXSpace $grabTicksH;
+                }
+            }
         }
     }