Ability to replace validated value in error message

[fan-tom]

When we are validating json agains json schema, it may contain user input (e.g.) text, that we want to avoid exposing in validation exception message. Currently we have an ability to customize the error message text using com.github.fge.jsonschema.cfg.ValidationConfiguration#validationMessages, where we can exclude the actual value that failed validation.
But it has to be done for each message template separately.
Instead it would be useful to postpone message rendering, which happens in com.github.fge.jsonschema.core.report.ProcessingMessage#addArgument until it is explicitly requested, which would allow us to replace the value value in message map with masked value (e.g. replace all non-space string character with *) in application code.