Validation errors should use WTForm's native error system

Currently the CreateReviewForm creates an error list, then on submit clears the list and adds the validation error to the list for it to be displayed:
However, WTForms have a native error dict, I have managed to get it working when validating individual fields, the following example would work:
```
def validate_name(self, name):
raise ValidationError("error")
```
I am yet to figure out how to do the same with the validate(self) method