DIFFEO-134: streamcorpus_directory tool

Give it a directory (or more) and it will process everything in that
directory with a common config file, by default creating rejester
jobs for all of them.
Fix streamcorpus_pipeline tool, require -i - for stdin

This is rationalizing the interface to match other tools.  Pass
--config configname (never a positional argument); --dump-config is
handled by yakonfig on its own
Don't nearly-silently fail deleting tmpdir on cleanup