Merge branch '17187-hover-row' into 'master'

Implement new row hover style

## What does this MR do?
Implement new row hover style

## What are the relevant issue numbers?
Closes #17187 

## Screenshots (if relevant)
![Screen_Shot_2016-06-01_at_1.40.04_PM](/uploads/62db01f405db50531fb648e46dc9598a/Screen_Shot_2016-06-01_at_1.40.04_PM.png)   

cc @dzaporozhets 

See merge request !4422

app/assets/stylesheets/framework/variables.scss

@@ -63,7 +63,8 @@ $gl-padding-top: 10px;
 /*
  * Misc
  */
-$row-hover: #f4f8fe;
+$row-hover: #f7faff;
+$row-hover-border: #b2d7ff;
 $progress-color: #c0392b;
 $avatar_radius: 50%;
 $header-height: 50px;

app/assets/stylesheets/pages/tree.scss

@@ -15,16 +15,23 @@
     margin-bottom: 0;
 
     tr {
-      > td, > th {
+      border-bottom: 1px solid $table-border-gray;
+      border-top: 1px solid $table-border-gray;
+
+      td, th {
         line-height: 23px;
       }
 
       &:hover {
+        cursor: pointer;
+
         td {
-          background: $row-hover;
+          background-color: $row-hover;
+          border-top: 1px solid $row-hover-border;
+          border-bottom: 1px solid $row-hover-border;
         }
-        cursor: pointer;
       }
+
       &.selected {
         td {
           background: $gray-dark;