Convert aiCamera to cc2DViewportObject

**Describe the solution you'd like**

When reading files that have cameras, convert them to cc2DViewportObjects in CC.

**Additional context**

Should implement something like this in `mioUtils`:
```c++
ccViewportParameters convertCameraToViewport( const aiCamera *inCamera, const aiMatrix4x4 &inTransform );
```

and then use it in `mioAbstractLoader` to create the cc2DViewportObjects.

Start by reading mioUtils and mioAbstractLoader, then trace how loaded cameras and cc2DViewportObjects are currently handled. Implement the requested camera-to-viewport conversion using the named function signature and use it in the loader so cameras from input files produce cc2DViewportObjects.

Written by the indexing model from the issue text.