Include childModalViewControllers when checking rmq.app.current_view_controller

I know the topic of detecting the _current_ view controller is a hairy one (I had my fair share of it).
But would it be possible to extend `rmq.app.current_view_controller` and in that respect `rmq.view_controller` to check and respect if a view has an active `childModalViewController`?

As it is right it's not possible to use `presentViewController` with any of both methods _if a there is currently a modal view controller on screen_.

I know it sounds strange but one real world use case would be displaying a `UIAlertController` from a modal view. I came across this while debugging a missing alert box from RedAlert.
Turns out `rmq.view_controller` is the culprit as it doesn't traverse down my modal VC resulting in an error like this:

```
Warning: Attempt to present on whose view is not in the window hierarchy!
```

`StartScreen` in this case is the VC below my current modal screen.
There's currently an [open issue](https://github.com/GantMan/RedAlert/issues/22) on this for RedAlert but IMHO the real fix belongs in RMQ.

Start by locating the implementations of rmq.app.current_view_controller and rmq.view_controller, then reproduce the modal-view case described in the issue with a UIAlertController. Done means both methods account for an active childModalViewController so presenting from the modal view no longer targets StartScreen below it.

Written by the indexing model from the issue text.