Called by the framework during form deserialization
to validate a form view. Default implementation validates each field
by calling 'validate-form-view-field', then if individual field validation
succeeds, applies view-global validators.

If this function succeeds validating the form it returns
true. Otherwise returns nil as the first value, and an association
list of either fields and errors or nils and errors (for non-field-related
validation errors) as the second value.

'object' - the object the form is being deserialized into.
'view' - form view object being deserialized.
'parsed-values' - an association list of field-info structures and
parsed values.