Allow to disable success logging

Thanks for this contribution, I'm working on getting it into the module.

It's in, I've disabled success logging by default because:

• It is largely just noise for most sites.
• We're only in beta, so I can kinda do what I like with changes etc.

Note that this will mean that existing sites upgrading to the latest versions of the Kraken module will stop logging successful conversions.

Automatically closed - issue fixed for 2 weeks with no activity.