Upgrade to latest Launch4j version and removed Launch4j code

Hi,
this branch contains two main modifications.

The Launch4j source code  is not included any more. Now there's an explict dependency in the pom.xml to the Launch4j artifact (I released it to Maven Central repository). So now it should be easier to manage upgrades to latest Launch4j versions.

The latest Launch4j version (3.4.0) is now used, instead of 3.0.0-pre2.