NEW Added type-based getAdvancedReportableFields
NEW Added type-based getAdvancedReportableFields

Allow the reported on object types to provide additional fields into the
query, which allows for some additional query capabilities. For example

```php
	return array(
            "TimedDay" => "DATE_FORMAT({$tableAlias}TimedAt, '%Y-%m-%d')"
        );
```

Will result in a TimedDay field being available in the result set, and for
being grouped on.

nyeholt/silverstripe-advancedreports,nyeholt/silverstripe-advancedreports