[srdf] Add contact surfaces to ground and pokeball.

srdf/ur_benchmark/ground.srdf

 <?xml version="1.0"?>
 <robot name="ground">
+  <contact name="surface">
+    <link name="ground_base"/>
+    <point>
+       1.00  1.00 0.0
+      -1.00  1.00 0.0
+      -1.00 -1.00 0.0
+       1.00 -1.00 0.0
+    </point>
+    <shape>
+      4 0 1 2 3
+    </shape>
+  </contact>
 </robot>

srdf/ur_benchmark/pokeball.srdf

@@ -4,4 +4,16 @@
     <position> 0 0 0 0.7071067811865476 0 0.7071067811865476 0 </position>
     <link name="base_link"/>
   </handle>
+  <contact name="bottom">
+    <link name="base_link"/>
+    <point>
+       0.01  0.01 -0.025
+      -0.01  0.01 -0.025
+      -0.01 -0.01 -0.025
+       0.01 -0.01 -0.025
+    </point>
+    <shape>
+      4 3 2 1 0
+    </shape>
+  </contact>
 </robot>