upgrade to xtext 2.15

Author: David Baum

generator/org.svis.generator.releng/pom.xml

@@ -28,7 +28,7 @@
 		<module>../org.svis.generator.run</module>
 	</modules>
 	<properties>
-		<xtext.version>2.13.0</xtext.version>
+		<xtext.version>2.15.0</xtext.version>
 		<mwe2.version>2.8.1</mwe2.version>
 		<emf.mwe>1.3.11</emf.mwe>
 		<clean.version>3.0.0</clean.version>
@@ -168,13 +168,6 @@
 					<groupId>org.eclipse.xtend</groupId>
 					<artifactId>xtend-maven-plugin</artifactId>
 					<version>${xtext.version}</version>
-					<dependencies>
-                        <dependency>
-                            <groupId>org.eclipse.platform</groupId>
-                            <artifactId>org.eclipse.equinox.common</artifactId>
-                            <version>3.10.0</version>
-                        </dependency>
-                    </dependencies>
 					<executions>
 						<execution>
 							<goals>