Add outputDirectory, finalName, classifier, and attach properties to Maven plugin

The following properties could be added to the IzPack Maven plugin to enhance its possibilities and make it work similar to the Maven Jar Plugin regarding its output:

*outputDirectory
Directory containing the generated JAR.
Default-value="$

"
*finalName
Name of the generated JAR.
Default-value="$

"
*classifier
Classifier to add to the artifact generated. If given, the artifact is attachable. Furthermore, the outputfile name gets -<classifier> as suffix.
If this is not given,it will merely be written to the output directory according to the finalName.
No default.
*enableAttachArtifact
Whether to attach the generated installer jar to the project as artifact, if a classifier was specified.
Default-value="true"
*enableOverrideArtifact
Whether to override the artifact file by the generated installer jar, if no classifier is specified.
This will set the artifact file to the given name based on outputDirectory + finalName or on output.

The given defaults make it compatible with the previous behavior.
The "output" property overrides outputDirectory, finalName, classifier, but should be marked deprecated .