Added missing migration 0010.

Hello. The present pull request adds a missing migration which was not present in the repository at all.

That provoked databases to mismatch what is defined in app models. As an example, the `FormDefinitionField.field_class` model field is declared with a `max_length` of 100 chars, but in the database it was creating a `varchar(32)` column. That lead to DB exceptions when trying to add some custom extra form fields.