'validationError' Common Field Property

[brownhoward]

User Story

As a Form Designer, I can define the error to be displayed if a user enters invalid data in a field (e.g., integer is out of range), so it is clear to the user how to correct the validation error.

Acceptance Criteria

1. In a Form Model, the 'validationError' property can be optionally defined for a data field, that defines the error message(s) that should be displayed is the entered data fails validation.
2. When the form is rendered, if the entered data is found to be invalid: a. If the 'validationError' property is defined, the custom validation error message is displayed. b. If the 'validationError' property is not defined, a generic validation error message is displayed.

Dev Notes

• validationError defined as a thing allowing the validation error messages in multiple languages to be defined: ui:validationError [ rdfs:label "Age must be 18 or older"@en ] ;

[brownhoward]

For consistency with #138, perhaps have a validation error thing:

    ui:validationError [ rdfs:label "Age must be 18 or older"@en ] ;