FR: Add a optional "camera speed" to Cutscenes->set-camera-target

One shortcoming of the set-camera-target is that it will instanly center on target, this is good for a scene cut, but if you want a camera to lock on a passing ship this is not good, you cant have the camera jumping on target, it would be nice to have something with a similar funtionality to the "turn time" in set-camera-facing that is only meant to be used on static objects.

Time will be not good here because the target is likely to me moving or start moving, so it needs to be a constant speed that the camera will use to try to center on target.

This is also usefull to make the camera constaly lagg behind the ship it tries to center on what is very usefull for flybys.