#9 support for xz utils

[toazz]

As .tar.xz files are getting more widely used, xarchiver could use xz utils to handle this kind of files, as well as for improved handling of .tar.lzma files, as p7zip can't deal with some of those. It should be a pretty easy task, because xz utils' command line interface is very similar to gzip.

[mase76]

Yes, support for xz compressed files would be welcome!