Add new config-option 'password_pbkdf2_default_rounds'... ...in 'main' section to configure the default parameter for new password generation. Set this to a higher value on faster systems which want more security. Thanks to Eli Collins for implementing this (see issue2550688). This now passes a config object (default None in which case we fall back to hard-coded parameters) into the password generation routine. This way we can add further parameters for password generation in the future. Also added a small regression test for this new feature.