[WIP] Support multiple @find-by annotations

Still open tasks but basic support for multiple ```@find-by```. Still requiring some new unit tests and ```ElementCollection``` see #48 for more details.

Closes #13
1. move out `parent::getIterator()` call to temp variable since it's used 2 times in this method
2. the `parent::` call gets you the `ArrayObject` class at all times (regular proxy or collection proxy); to make this more obvious just replace `parent::` with `ArrayObject::`