Support for 'ofType()' function for monomorphic collections

E..g. ```Patient.name.given.ofType(string)```


Simple exclusions:

**Details**

```Expected: WrappedArray(Peter, James) but got: null ==> expected: <WrappedArray(Peter, James)> but was: <null>```
- ```Patient.name.given.ofType(string) [ofType() function for the null element of a collection (2)]```

