Default parameter

1. All camera objects created have an empty object parent, a key frame for multi-axis motion in animation
2. If the object is selected, the camera is created 10 meters away from the -Y axis of the selected object by 
    default.If there is no selected object, the camera is created in place
3. All camera objects created will obtain the current frame range of the scene, and automatically enter the 
    key frame in the first and last frame to create animation.