Hide sensitive properties from toString()

[Michal-Kubricht]

It is in some cases useful to mark some property in JSON schema definition as a sensitive (or confidential) and thus making it hidden from generated toString() method.

Generator already contains a feature "toStringExcludes" which is global property specifying everything to be excluded from toString generation by name.

It would be advantage to have a definition of what to exclude inside the JSON schema. Idea would be to have it similarly to already existing feature excludedFromEqualsAndHashCode.

[Michal-Kubricht]

Attempt to bring the feature: #1557