DeleteWithRelatedData does not delete children

**Description:**
`DeleteQuery, U>`
```
/**
* Delete all instances and their related data that match the query.
*/
void deleteWithRelatedData();
```
does not delete child process instances and tasks.

**Expected behavior:**
All related data will be deleted.

**Code**
[jUnit test](https://github.com/martin-grofcik/flowable-engine/tree/%233289_deleteWithRelatedData)

Start with the DeleteQuery, U> declaration and inspect the linked JUnit test for issue #3289. Trace deleteWithRelatedData() and verify that deleting matching instances also removes child process instances and tasks; done means all related data is deleted.

Scritto dal modello di indicizzazione a partire dal testo della issue.