fix TypeAssigner

1) lab3:fieldSQLInjection1 - it does not type precisely - but creates casts for all further usages of $stack8

```
    $stack8 = new target.hidden.exercise2and3.FieldSQLInjection1$ObjectWithTaint;
```

2) does not type single defs - but casts them - so the information seems to be gathered

3) splits a single assignment into 2 varibles (maybe connected with 2) ?)