Version 0.20.0

Added

• Add DurationField.
• Allow passing max_digits to FloatField.
• Add local_or function to QuerySets.

Changed

• Only the main table of a queryset is queryable via model_class.columns.foo == foo. Select related models have now an unique name for their path.
  The name can be retrieved via tables_and_models or using f"{hash_tablekey(...)}_{column}".
• Breaking: Alter tables_and_models to use the prefix as key with '' for the maintable and model.
• Breaking: Functions passed to filter functions reveive now a second positional parameter tables_and_models.
• build_where_clause conditionally uses a subquery.
• Rename QueryType to QuerySetType. The old name stays as an alias.
• The debug property of QuerySet named sql inserts now the blanks and uses the dialect.

Fixed

• Triggering load on non-existent field when reflecting.
• InspectDB mapping was incorrect.
• Fix query edge cases.
• Fix using related queries with update/delete.