Use newer Proguard that can handle JDK14.

Unfortunately due to a bug in proguard-maven-plugin I can't currently use a
version of Proguard that supports JDK15.

launcher/pom.xml

@@ -85,7 +85,7 @@
       <plugin>
         <groupId>com.github.wvengen</groupId>
         <artifactId>proguard-maven-plugin</artifactId>
-        <version>2.0.14</version>
+        <version>2.3.1</version>
         <executions>
           <execution>
             <phase>package</phase>
@@ -94,14 +94,14 @@
         </executions>
         <dependencies>
           <dependency>
-            <groupId>net.sf.proguard</groupId>
+            <groupId>com.guardsquare</groupId>
             <artifactId>proguard-base</artifactId>
-            <version>6.1.0</version>
+            <version>7.0.0</version>
             <scope>runtime</scope>
           </dependency>
         </dependencies>
         <configuration>
-          <proguardVersion>6.1.0</proguardVersion>
+          <proguardVersion>7.0.0</proguardVersion>
           <outputDirectory>${project.build.directory}</outputDirectory>
           <outjar>${project.build.finalName}.jar</outjar>
           <injar>${project.build.finalName}.jar</injar>