[Releng] Included unleash-maven-plugin to simplify releases

In order to ensure a smooth process for future releases, Eclipse Capra
is now using the unleash-maven-plugin that supports changing the versions
of all artifacts to the release version, creating a release tag, and
switching to a new development version in one single run of Maven.
The concrete procedure we use to achieve this can be found at:
https://wiki.eclipse.org/Capra/PreparingForRelease

pom.xml

diff --git a/pom.xml b/pom.xml
index 9098b2c..9633fbe 100644
--- a/pom.xml
+++ b/pom.xml
@@ -1,5 +1,4 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<!--
+<?xml version="1.0" encoding="UTF-8" standalone="no"?><!--
 	Copyright (c) 2016 Chalmers | University of Gothenburg, rt-labs and others.
 	All rights reserved. This program and the accompanying materials
 	are made available under the terms of the Eclipse Public License v1.0
@@ -8,11 +7,7 @@
 
 	Contributors:
 		Chalmers | University of Gothenburg and rt-labs - initial API and implementation and/or initial documentation
--->
-
-<project
-	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"
-	xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
+--><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/xsd/maven-4.0.0.xsd">
 	<modelVersion>4.0.0</modelVersion>
 
 	<groupId>org.eclipse.capra</groupId>
@@ -55,7 +50,7 @@
 		<module>tests/org.eclipse.capra.testsuite</module>
 		<module>tests/org.eclipse.capra.handler.cdt.tests</module>
 		<module>tests/org.eclipse.capra.handler.jdt.tests</module>
-        	<module>tests/org.eclipse.capra.handler.uml.tests</module>
+		<module>tests/org.eclipse.capra.handler.uml.tests</module>
         
 		
 		<!-- Features -->
@@ -111,6 +106,12 @@
 			<layout>default</layout>
 		</repository>
 	</repositories>
+	
+	 <scm>
+       <connection>scm:git:https://git.eclipse.org/r/capra/org.eclipse.capra.git</connection>
+       <developerConnection>scm:git:https://git.eclipse.org/r/capra/org.eclipse.capra.git</developerConnection>
+       <tag>HEAD</tag>
+   </scm>
 
 	<build>
 		<plugins>
@@ -181,6 +182,19 @@
 					</environments>
 				</configuration>
 			</plugin>
+			
+			<plugin>
+				<groupId>com.itemis.maven.plugins</groupId>
+				<artifactId>unleash-maven-plugin</artifactId>
+				<version>2.9.3</version>
+				<dependencies>
+					<dependency>
+						<groupId>com.itemis.maven.plugins</groupId>
+						<artifactId>unleash-scm-provider-git</artifactId>
+						<version>2.2.0</version>
+					</dependency>
+				</dependencies>
+			</plugin>
 		</plugins>
 	</build>
 </project>