Provide an ability to pass custom Archiver to ArchiverCompressorDecorator

[hvarakhobava]

Hi,

It is very desirable to have an ability to pass own implementation of Archiver interface to ArchiverCompressorDecorator.
Since the last one is package-private, please either make it public or make a new static factory method in ArchiverFactory as follow:

public static Archiver createArchiver(Archiver archiver, CompressionType compression) {
// do stuff
}

[thrau]

ArchiverCompressorDecorator only take CommonsArchiver instances, which are also package private. I don't see much harm in making the classes public, but jarchivelib wasn't designed to be open to extensions and alternative archive providers, which is why the API exposure is minimal.