Upgrade Maven plugins to enable Java 11 compilation.

pom.xml

@@ -33,7 +33,7 @@
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
         <java.version>1.8</java.version>
-        <powermock.version>2.0.2</powermock.version>
+        <powermock.version>2.0.4</powermock.version>
         <!-- More visible way how to change dependency versions -->
         <spigot.version>1.15.2-R0.1-SNAPSHOT</spigot.version>
         <bentobox.version>1.15.4</bentobox.version>
@@ -137,7 +137,7 @@
         <dependency>
             <groupId>org.mockito</groupId>
             <artifactId>mockito-core</artifactId>
-            <version>3.0.0</version>
+            <version>3.1.0</version>
             <scope>test</scope>
         </dependency>
         <dependency>
@@ -213,7 +213,7 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-compiler-plugin</artifactId>
-                <version>3.7.0</version>
+                <version>3.8.1</version>
                 <configuration>
                     <source>${java.version}</source>
                     <target>${java.version}</target>
@@ -222,21 +222,24 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-surefire-plugin</artifactId>
-                <version>2.22.0</version>
+                <version>2.22.2</version>
             </plugin>
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-jar-plugin</artifactId>
-                <version>3.1.0</version>
+                <version>3.2.0</version>
             </plugin>
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-javadoc-plugin</artifactId>
-                <version>3.0.1</version>
+                <version>3.1.1</version>
                 <configuration>
+                    <source>8</source>
                     <show>public</show>
                     <failOnError>false</failOnError>
                     <additionalJOption>-Xdoclint:none</additionalJOption>
+                    <!-- To compile with Java 11, this tag may be required -->
+                    <!-- <javadocExecutable>${java.home}/bin/javadoc</javadocExecutable> -->
                 </configuration>
                 <executions>
                     <execution>
@@ -295,9 +298,14 @@
             <plugin>
                 <groupId>org.jacoco</groupId>
                 <artifactId>jacoco-maven-plugin</artifactId>
-                <version>0.8.1</version>
+                <version>0.8.4</version>
                 <configuration>
                     <append>true</append>
+                    <excludes>
+                        <!-- This is required to prevent Jacoco from adding 
+                            synthetic fields to a JavaBean class (causes errors in testing) -->
+                        <exclude>**/*Names*</exclude>
+                    </excludes>
                 </configuration>
                 <executions>
                     <execution>