Update JsonSchemaGeneratorV4.java (minLength & maxLength)

Hello Danilo,

I am using JJSchema and I have found a bug in file "JsonSchemaGeneratorV4.java":

if (props.minLength() > 0) {
schema.put("minLength", props.minItems());
}
if (props.maxLength() > -1) {
schema.put("maxLength", props.maxItems());
}

As you can see, when you put the properties minLength and maxLength in the schema, you are using minItems and maxItems instead the correct properties.

I have seen that you correct the same bug in file "PropertyWrapper.java" so I think it works in v1 but not in v4.

Best regards, Eduardo.