Fix a bug in the table metadata caching mechanism; we were caching in Model::_field_types rather than the child version. Since this is an internal mechanism of Model, it is never overridden in the child, which would be necessary to make the prior version work. Instead, we cache in Model::_field_types[_table_name] since the table name will always be overridden and is thus accessible via static::_table_name.
Fix a bug in the table metadata caching mechanism; we were caching in Model::_field_types rather than the child version. Since this is an internal mechanism of Model, it is never overridden in the child, which would be necessary to make the prior version work. Instead, we cache in Model::_field_types[_table_name] since the table name will always be overridden and is thus accessible via static::_table_name.

briancline/spire