Simplify JDK and Maven installation and version upgrading.

java-tools.properties now defines versions in a machine readable format so that we can install these versions into the Docker image verify those versions in our release tooling to ensure the environment matches what we expect.

Closes #32

ci/java-init.sh

@@ -0,0 +1,32 @@
+#!/bin/bash
+
+####################################################################
+# Utility to install Java and Maven into the build container image #
+####################################################################
+
+source $HOME/.sdkman/bin/sdkman-init.sh
+JAVA_TOOLS_PROPERTIES=java-tools.properties
+
+if [ ! -f ${JAVA_TOOLS_PROPERTIES} ]
+then
+    echo "File does not exist: ${JAVA_TOOLS_PROPERTIES}"
+    exit 1
+fi
+
+while IFS='=' read -r key value
+do
+    key=$(echo $key | tr '.' '_')
+    eval ${key}=\${value}
+done < "${JAVA_TOOLS_PROPERTIES}"
+
+IFS=', ' read -r -a jdk_versions <<< "$jdks"
+
+for to_install in "${jdk_versions[@]}"
+do
+  dist="${to_install}-tem"
+  echo "Installing JDK ${dist}"
+  yes | sdk install java "${dist}"
+done
+
+echo "Installing Maven ${maven}"
+yes | sdk install maven ${maven}