Upgrade plugins, add enforcer plugin

pom.xml

@@ -70,7 +70,7 @@
 			<plugin>
 				<groupId>org.apache.maven.plugins</groupId>
 				<artifactId>maven-gpg-plugin</artifactId>
-				<version>1.5</version>
+				<version>1.6</version>
 				<executions>
 					<execution>
 						<id>sign-artifacts</id>
@@ -84,7 +84,7 @@
 			<plugin>
 				<groupId>org.apache.maven.plugins</groupId>
 				<artifactId>maven-antrun-plugin</artifactId>
-				<version>1.6</version>
+				<version>1.8</version>
 				<executions>
 					<execution>
 						<id>prepare</id>
@@ -94,8 +94,7 @@
 						</goals>
 						<configuration>
 							<target>
-								<taskdef resource="net/sf/antcontrib/antlib.xml"
-									classpathref="maven.plugin.classpath" />
+								<taskdef resource="net/sf/antcontrib/antlib.xml" classpathref="maven.plugin.classpath" />
 								<for param="filepath">
 									<path>
 										<fileset dir="src/main/resources" includes="*.knxproj" />
@@ -132,7 +131,7 @@
 			<plugin>
 				<groupId>com.soebes.maven.plugins</groupId>
 				<artifactId>iterator-maven-plugin</artifactId>
-				<version>0.3</version>
+				<version>0.5.0</version>
 				<executions>
 					<execution>
 						<phase>process-resources</phase>
@@ -173,6 +172,29 @@
 					</execution>
 				</executions>
 			</plugin>
+			<plugin>
+				<groupId>org.apache.maven.plugins</groupId>
+				<artifactId>maven-enforcer-plugin</artifactId>
+				<version>3.0.0-M2</version>
+				<executions>
+					<execution>
+						<id>enforce-versions</id>
+						<goals>
+							<goal>enforce</goal>
+						</goals>
+						<configuration>
+							<rules>
+								<requireMavenVersion>
+									<version>3.5.3</version>
+								</requireMavenVersion>
+								<requireJavaVersion>
+									<version>1.8</version>
+								</requireJavaVersion>
+							</rules>
+						</configuration>
+					</execution>
+				</executions>
+			</plugin>
 		</plugins>
 	</build>
 </project>