Rotate camera by degrees or transformation matrix

**Is your feature request related to a problem? Please describe.**

Say, I got a triangle mesh, I may want to bring the bottom tiangle to the front. The current mesh visualization can only rotate the camera with specified mouse events with `vis.get_view_control().rotate`, which can hardly be accurate.

I am working on an animition application that oftenly require to change the camera pose to look at different areas during the process. Is there any good suggestions? It would be the best if we can have the API to perform accurate rotation, say, by angles.

Thanks