added gwt-visualization dependency to pom.xml to make gwt maven plugin find it

java/com.sap.sailing.gwt.ui/pom.xml

@@ -39,6 +39,13 @@
     	<version>1.1.0</version>
     	<scope>provided</scope>
     </dependency>
+    <dependency>
+        <!-- This dependency is required because the GWT Maven Plugin searches other GWT modules only in Maven dependencies -->
+    	<groupId>com.google.code</groupId>
+    	<artifactId>gwt-visualization</artifactId>
+    	<version>1.1.0</version>
+    	<scope>provided</scope>
+    </dependency>
   </dependencies>
 
   <build>