Update dependencies and Maven plugins

Dependencies:
 - SLF4J-Log4j 1.7.12
 - JUnit 4.12

Maven plugins:
 - maven-compiler-plugin 3.6.0
 - maven-jar-plugin 3.0.2
 - maven-surefire-plugin 2.19.1
 - maven-dependency-plugin 2.10
 - maven-assembly-plugin 3.0.0
 - maven-release-plugin 2.5.3
 - maven-javadoc-plugin 2.10.4
 - maven-source-plugin 3.0.1
 - maven-gpg-plugin 1.6
 - buildnumber-maven-plugin 1.4

After updating the maven-assembly-plugin it is no longer necessary to
fix the versions of plexus-archiver and plexus-io used by the plugin.

Author: cboehme

pom.xml

@@ -85,7 +85,7 @@
 			<plugin>
 				<groupId>org.apache.maven.plugins</groupId>
 				<artifactId>maven-compiler-plugin</artifactId>
-				<version>2.3.2</version>
+				<version>3.6.0</version>
 				<configuration>
 					<source>${targetJdk}</source>
 					<target>${targetJdk}</target>
@@ -96,7 +96,7 @@
 			<plugin>
 				<groupId>org.apache.maven.plugins</groupId>
 				<artifactId>maven-jar-plugin</artifactId>
-				<version>2.3.1</version>
+				<version>3.0.2</version>
 				<configuration>
 					<archive>
 						<manifest>
@@ -117,13 +117,13 @@
 			<plugin>
 				<groupId>org.apache.maven.plugins</groupId>
 				<artifactId>maven-surefire-plugin</artifactId>
-				<version>2.10</version>
+				<version>2.19.1</version>
 			</plugin>
 
 			<plugin>
 				<groupId>org.codehaus.mojo</groupId>
 				<artifactId>buildnumber-maven-plugin</artifactId>
-				<version>1.1</version>
+				<version>1.4</version>
 				<executions>
 					<execution>
 						<phase>validate</phase>
@@ -136,7 +136,7 @@
 
 			<plugin>
 				<artifactId>maven-dependency-plugin</artifactId>
-				<version>2.8</version>
+				<version>2.10</version>
 				<executions>
 					<execution>
 						<id>unpack-metafacture-core-resources</id>
@@ -159,23 +159,7 @@
 
 			<plugin>
 				<artifactId>maven-assembly-plugin</artifactId>
-				<version>2.4</version>
-				<dependencies>
-					<!-- Pin the versions of plexus-archiver and plexus-io as
-					     there are apparently two bugs in the versions on which
-					     maven-assembly-plugin depends on by default. See
-					     http://www.misanthropicgeek.net/?p=1303 for details. -->
-					<dependency>
-						<groupId>org.codehaus.plexus</groupId>
-						<artifactId>plexus-archiver</artifactId>
-						<version>2.4.3</version>
-					</dependency>
-					<dependency>
-						<groupId>org.codehaus.plexus</groupId>
-						<artifactId>plexus-io</artifactId>
-						<version>2.0.8</version>
-					</dependency>
-				</dependencies>
+				<version>3.0.0</version>
 				<executions>
 					<execution>
 						<id>create-distribution-package</id>
@@ -205,12 +189,11 @@
 			<plugin>
 				<groupId>org.apache.maven.plugins</groupId>
 				<artifactId>maven-release-plugin</artifactId>
-				<version>2.4</version><!--$NO-MVN-MAN-VER$ -->
+				<version>2.5.3</version><!--$NO-MVN-MAN-VER$ -->
 				<!-- m2e complains about a different plugin version being specified in
 					the parent pom. However, this is not actually problem for maven. So, we can
 					ignore the warning. -->
 			</plugin>
-
 		</plugins>
 	</build>
 
@@ -233,7 +216,7 @@
 		<dependency>
 			<groupId>org.slf4j</groupId>
 			<artifactId>slf4j-log4j12</artifactId>
-			<version>1.7.6</version>
+			<version>1.7.21</version>
 		</dependency>
 
 		<!-- The following dependencies are placed in the "provided"
@@ -268,7 +251,7 @@
 		<dependency>
 			<groupId>junit</groupId>
 			<artifactId>junit</artifactId>
-			<version>4.11</version>
+			<version>4.12</version>
 			<scope>test</scope>
 		</dependency>
 
@@ -282,7 +265,7 @@
 					<plugin>
 						<groupId>org.apache.maven.plugins</groupId>
 						<artifactId>maven-javadoc-plugin</artifactId>
-						<version>2.8</version>
+						<version>2.10.4</version>
 						<executions>
 							<execution>
 								<id>attach-javadocs</id>
@@ -300,7 +283,7 @@
 					<plugin>
 						<groupId>org.apache.maven.plugins</groupId>
 						<artifactId>maven-source-plugin</artifactId>
-						<version>2.1.2</version>
+						<version>3.0.1</version>
 						<executions>
 							<execution>
 								<id>attach-sources</id>
@@ -314,7 +297,7 @@
 					<plugin>
 						<groupId>org.apache.maven.plugins</groupId>
 						<artifactId>maven-gpg-plugin</artifactId>
-						<version>1.4</version>
+						<version>1.6</version>
 						<executions>
 							<execution>
 								<id>sign-artifacts</id>