(ui) upgrade d3/nvd3

(cherry picked from commit 8decc7a3)

src/opnsense/www/css/nv.d3.css

-/* nvd3 version 1.8.2 (https://github.com/novus/nvd3) 2016-01-24 */
+/* nvd3 version 1.8.3 (https://github.com/novus/nvd3) 2016-04-26 */
 .nvd3 .nv-axis {
     pointer-events:none;
     opacity: 1;
@@ -164,6 +164,18 @@
 }
 
 
+.nv-force-node {
+  stroke: #fff;
+  stroke-width: 1.5px;
+}
+.nv-force-link {
+  stroke: #999;
+  stroke-opacity: .6;
+}
+.nv-force-node text {
+  stroke-width: 0px
+}
+
 .nvd3 .nv-legend .nv-disabled rect {
     /*fill-opacity: 0;*/
 }
@@ -333,6 +345,16 @@ svg.nvd3-svg {
     fill-opacity: .7;
 }
 
+/**********
+*  Print
+*/
+
+@media print {
+  .nvd3 text {
+    stroke-width: 0;
+    fill-opacity: 1;
+  }
+}
 
 .nvd3.nv-ohlcBar .nv-ticks .nv-tick {
     stroke-width: 1px;