Add an example robot with a cornelius joint

VirtualRobot/data/robots/examples/RrtDemo/Joint3Cornelius.xml

+<?xml version="1.0" encoding="UTF-8" ?>
+
+<Robot Type="Simple3DoFRobotWithCorneliusJoint" StandardName="Simple3DoFRobotWithCorneliusJoint" RootNode="Start">
+	
+	<RobotNode name="Start">
+		<Visualization enable="false">
+			<CoordinateAxis enable="true" scaling="1" text="Root"/>
+		</Visualization>
+		<Child name="Joint1"/>
+	</RobotNode>
+
+	<RobotNode name="Joint1">
+		<Joint type="revolute">
+			<Limits unit="degree" lo="-90" hi="90"/>
+            <!--DH a="300" d="0" theta="0" alpha="90" units="degree"/-->
+        </Joint>
+		<Visualization enable="true">
+			 <File type="Inventor">joint_rot_sphere.iv</File>
+			 <UseAsCollisionModel/>
+		</Visualization>
+        <Child name="Joint2Cornelius"/>
+	</RobotNode>
+
+    <RobotNode name="Joint2Cornelius">
+		<Transform>
+			<DH a="300" d="0" theta="0" alpha="90" units="degree"/>
+		</Transform>
+        <Joint type="cornelius">
+			<Limits unit="degree" lo="0" hi="360"/>
+            <!--DH a="300" d="0" theta="0" alpha="0" units="degree"/-->
+        </Joint>
+		<Visualization enable="true">
+			 <File type="Inventor">joint_rot_sphere.iv</File>
+			 <UseAsCollisionModel/>
+		</Visualization>
+        <Child name="Joint3"/>
+	</RobotNode>
+
+    <RobotNode name="Joint3">
+		<Transform>
+			<DH a="300" d="0" theta="0" alpha="0" units="degree"/>
+		</Transform>
+        <Joint type="revolute">
+			<Limits unit="degree" lo="-90" hi="90"/>
+        </Joint>
+		<Visualization enable="true">
+			 <File type="Inventor">joint_rot_sphere.iv</File>
+			 <UseAsCollisionModel/>
+		</Visualization>
+		<Child name="EndPoint"/>
+	</RobotNode>
+
+	<RobotNode name="EndPoint">
+		<Transform>
+			<DH a="300" d="0" theta="0" alpha="0" units="degree"/>
+		</Transform>
+		<Visualization enable="true">
+			 <File type="Inventor">sphere.iv</File>
+			 <UseAsCollisionModel/>
+		</Visualization>
+	</RobotNode>
+
+	<RobotNodeSet name="AllJoints" kinematicRoot="Joint1">
+		<Node name="Joint1"/>
+        <Node name="Joint2Cornelius"/>
+        <Node name="Joint3"/>
+	</RobotNodeSet>
+
+	<RobotNodeSet name="CollisionModel">
+		<Node name="Joint1"/>
+        <Node name="Joint2Cornelius"/>
+        <Node name="Joint3"/>
+  	<Node name="EndPoint"/>
+	</RobotNodeSet>
+
+</Robot>