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