Add ability to disable comments if no vulnerabilities found

[jamesrelder]

Our developers are complaining of too many emails for MRs due to the Frogbot comments when no vulnerabilities are found. Now whilst I don't agree with them entirely about this as I think it's important to have the status on the MR even when nothing bad is found, we need happy developers.

So please could you implement a flag, maybe something like JF_SUCCESS_COMMENT with a boolean value true/false that would disable the commenting on MRs if no vulnerabilities are found?

Thanks! James