POM: factor out the jython version to a property

Author: ctrueden

pom.xml

@@ -30,6 +30,9 @@
 		<license.copyrightOwners>Board of Regents of the University of
 Wisconsin-Madison, Broad Institute of MIT and Harvard, and Max Planck
 Institute of Molecular Cell Biology and Genetics.</license.copyrightOwners>
+
+		<jython.version>2.5.3</jython.version>
+		<jython-shaded.version>${jython.version}</jython-shaded.version>
 	</properties>
 
 	<developers>
@@ -87,7 +90,7 @@ Institute of Molecular Cell Biology and Genetics.</license.copyrightOwners>
 		<dependency>
 			<groupId>org.scijava</groupId>
 			<artifactId>jython-shaded</artifactId>
-			<version>2.5.3</version>
+			<version>${jython-shaded.version}</version>
 		</dependency>
 
 		<!-- Test dependencies -->