allow help() called from other functions

...sparked by ball not reporting anything when no package specified
help() to use *args

makes all args a list automatically, no need to test if string. Change
download to use help()
pep8 do_download() -- but it's broken

A casualty of getting rid of get_ball in favour of get_info. Am now
second guessing that move, because `get_info(packagename)['local_zip']`
is arguably worse (overly verbose) than `get_ball(packagename)`. What
I'd really like is `info.gdal.zipfile` and `info.gdal.url_zipfile`
access dicts with dotted notation

AttrDict class from Stack Overflow, plus a simple test that shows it does indeed do the job. Much more testing and usage circumstances needed to be confident about it.
download fixed

using new dotted notation. clean up still needed