Multi PhantomCameraHost / Split Screen Setup Support

[ramokz]

Context

Idea is to support split screen views using multiple PhantomCameraHost - each attached to separate Cameras (2D or 3D).

Proposed Solution

When more than 1 PhantomCameraHost is added to a scene, add a dropdown property option for each PhantomCamera (to use within the Editor), which allows the user to decide which PhantomCamera belongs to which PhantomCameraHost. Each PhantomCameraHost will then only respond to the changes for the PhantomCameras that are assigned to it.