billing: Fix compression of error files

The billing indexer forgot to compress error files as part of the
nightly run.

I also added support for multi-argument invocation for several
commands.

Target: trunk
Request: 2.7
Require-notes: no
Require-book: no
Acked-by: Paul Millar <paul.millar@desy.de>
Patch: http://rb.dcache.org/r/6235/