Updates the build number to 0.3.1 for the next patch release

Updates the build script for conditional compilation using either Java
8 or Java 9 options.  Java 9 deprecated the java.xml.bind package and
removed it as a default Java SE package, so we have to reference it via
the --add-modules argument.

Updates the linux/mac launch script to check the java runtime version
and use either a Java 8 or Java 9 launch command.

scripts/run_sdrtrunk_linux.sh

@@ -1,2 +1,16 @@
 #!/bin/bash
-java -XX:+UseG1GC -cp "*:libs/*" gui.SDRTrunk
+
+java -version
+
+# Test for java version 9
+JAVA_9=$(java -version 2>&1 | grep -i version | sed 's/.* "\([9]\).*/\1/')
+
+if [ -z ${JAVA_9+x} ]; then
+  echo Using Java 9 program options
+  # Java 9 uses the G1 garbage collector by default and requires that we specify the
+  # java.xml.bind package since it's been removed from the java se core library
+  java -cp "*:libs/*" --add-modules java.xml.bind gui.SDRTrunk;
+else
+  echo Using Java 8 program options
+  java -XX:+UseG1GC -cp "*:libs/*" gui.SDRTrunk;
+fi