Show Data Tile checkboxes only on hover or if selected

According to patternfly specs (draft) checkboxes should only be shown
in data tiles when hovered over the tile or if selected.

Author: jeff-phillips-18

dist/styles/angular-patternfly.css

@@ -215,12 +215,13 @@
   width: 260px;
 }
 
-.tiles-view-pf .tile-check-box {
+.tiles-view-pf .tile .tile-check-box {
   left: 10px;
   position: absolute;
   top: 8px;
   width: 20px;
   z-index: 3;
+  visibility: hidden;
 }
 
 .tiles-view-pf .tile-content {
@@ -257,6 +258,10 @@
 .tiles-view-pf .tile.active:focus .pficon {
   color: #ffffff;
 }
+.tiles-view-pf .tile:hover .tile-check-box,
+.tiles-view-pf .tile.active .tile-check-box {
+  visibility: visible;
+}
 
 .tiles-view-pf .tile.disabled, .tile.disabled:hover, .tile.disabled:focus {
   border: 1px solid #eee;

dist/styles/angular-patternfly.min.css

@@ -215,12 +215,13 @@
   width: 260px;
 }
 
-.tiles-view-pf .tile-check-box {
+.tiles-view-pf .tile .tile-check-box {
   left: 10px;
   position: absolute;
   top: 8px;
   width: 20px;
   z-index: 3;
+  visibility: hidden;
 }
 
 .tiles-view-pf .tile-content {
@@ -257,6 +258,10 @@
 .tiles-view-pf .tile.active:focus .pficon {
   color: #ffffff;
 }
+.tiles-view-pf .tile:hover .tile-check-box,
+.tiles-view-pf .tile.active .tile-check-box {
+  visibility: visible;
+}
 
 .tiles-view-pf .tile.disabled, .tile.disabled:hover, .tile.disabled:focus {
   border: 1px solid #eee;