Support extraction of XZ archives in archive.extracted state
Support extraction of XZ archives in archive.extracted state

Using an XZ-compressed archive with archive.extracted raises a
tarfile.ReadError exception, as only gzip and bzip2 are supported by
tarfile. This commit catches that exception and attempts to extract
using xz-utils, if present.

It also makes some clarifications and corrections to the documentation.

saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt