Add support for UIPickerViews in Subliminal

UIPickerViews are under a different Window other than keyWindow, so I had to find the other one.  Otherwise it is pretty straightforward.  I'm leaning on the UIA methods a bit more heavily for interacting with the element, but open to suggestions.

Added one fairly comprehensive test case.
Rather than documenting the exception in the method discussion like this, please use the "@exception" syntax:

```
@exception SLUIAElementAutomationException Raised if _title_ is not a valid value for the specified component.
```