Until urlbrabber is gone completely, the urlgrabber.progress must stay.
logging: TransactionDisplay.errorlog() logs to stderr.

Else we can be missing important failures and that can get painful.

The commit also merges NoOutputTransactionDisplay and TransactionDisplay
into one class, they don't make sense separately.
Add '--nocrypto' tsflag config value.

Allows transaction to pass when NSS in RPM is broken.

Related: RhBug:1006280
Related: RhBug:1006287
reimplement urlopen() on top of librepo
remove all users of urlgrabber.url{open,read}

repo._default_grabopts() must have been failing with AttributeError,
so I've used urlgrabber_opts() instead.
download_packages() cleanup
add dnf.cli.progress.MultiProgressMeter
use librepo.download_packages() and MultiProgressMeter