[NO-STORY] Add green material for gzweb

Change-Id: I52213e97e35f1ac05ed00714acc7db6dad3792d9

http/client/assets/materials/green.material

+material Gazebo/Green
+{
+  technique
+  {
+    pass ambient
+    {
+      ambient 0 1 0
+      diffuse 0 1 0
+      specular 0.1 0.1 0.1 1 1
+    }
+  }
+}
+