Support cutting relative top level directory when extracting files from archive

[abarsov]

This is mostly about signature of overloaded extract methods. Those might declare additional parameter with relative path that should be cut off while extracting.

[thrau]

could you provide a unzip or tar command that does this? this helps me think about how to extend the api.

[abarsov]

There is a similar option for tar --strip-components. Though it simply cut top level directories.