#4 validator: using errorcodes

[holger]

instead of keeping the error-code description in the
validator it should rely on some error codes that can
be resolved using some resource bundle.

[Marin Dimitrov]

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why is that necessary?

[Nathalie Steinmetz]

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This is necessary because currently all results that come
back from the validator are based on plain text strings.
These can neither be localized nor changed by the resulting
application without using .equals or using regular expressions.

Even if these solutions where to be employed they would
break as soon as a new message was added or an existing one
changed.