Add a script to compress old expinfo directories.
Run it as "archive-expinfo [-t threshold]", where "threshold" is the number of days experiments must have been inactive to be compressed (defaulting to 1000). Directories will be tarred and compressed in place. For example, if /usr/testbed/expinfo/testbed/example/1234 has been inactive for longer than the threshold, its entire contents will be archived in /usr/testbed/expinfo/testbed/example/1234.tar.bz2 and the original directory removed. The compression is extremely efficient, typically reducing directories to around 2% of their original size.