Improve setting keypoints for cinematics

Please implement an option to navigate by using arrow keys while setting up keypoints when making a cinematic, whitout moving the camera angle. This would make it a lot easier to create new cinematics.

For related information please look at this forum post (Dutch only):

https://community.tygron.com/forum/discussion/256/cinematics-keypoints-position-changing/p1

On this wiki page multiple “How to’s” are available:

https://previewsupport.tygron.com/wiki/Cinematic