Allow overwriting the java path

[Blokje5]

The project.clj specifies the jdk path directly, meaning it will only work on ubuntu installations. For example, in alpine, the default jdk path is /usr/lib/jvm/java-1.8-openjdk/ and not /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java. I am not familiar with Leiningen and Clojure, but there should be a better way then either overriding the project.clj or creating a profiles.clj and moving that in the project directory.