function validateInput (value) {
	// undefined values are always valid
	if (value === undefined || value === null || value === '') return true;
	// If a string is provided, check it is an upload or delete instruction
	// TODO: This should really validate files as well, but that's not pased to this method
	if (typeof value === 'string' && /^(upload\:)|(delete$)|(data:[a-z\/]+;base64)|(https?\:\/\/)/.test(value)) return true;
	// If the value is an object and has a cloudinary public_id, it is valid
	if (typeof value === 'object' && value.public_id) return true;
	// None of the above? we can't recognise it.
	return false;
}
Detects whether the field has been modified