Task #1771: updated maven POM file.

JAVA/GUI/Plotter/pom.xml

 <?xml version="1.0" encoding="UTF-8"?>
 
-<project>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
+
 	<modelVersion>4.0.0</modelVersion>
 	<groupId>nl.astron.lofar.gui</groupId>
 	<artifactId>plotter</artifactId>
@@ -11,6 +13,7 @@
 		<name>Astron</name>
 		<url>http://www.astron.nl</url>
 	</organization>
+	
 	<properties>
 		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
 		<project.test.sourceEncoding>UTF-8</project.test.sourceEncoding>