Let blobs un archive

I noticed that in 1.x trying to unzip/untar etc an archive does not work because '.' is not allowed in the names of blobs.  To work around this we will match either '_' or '.' in the name of a blob when deciding how to decompress it.

At the same time I cleaned up the unzip/unjar code to make it more common, and added in support to the java untar to support symlinks and permissions.  At some point in the future we could then remove the shell version of untar.