Packaging non binded classes

Adding a step to optionally package non binded classes in a jar.
The feature can be enabled through the generateUnbidedJar switch
added to this plugin DSL extension and the jar name can be specified
through unbindedJarName.

example :

JIBXBinding {
	generateUnbindedJar = true
	unbindedJarName = 'my-unbinded-classes.jar'
}

Change-Id: I9f4f7b236ee5ccd64c86373a026cd8a278282bbd