Add getters for camera parameters

[Nokse22]

Is your feature request related to a problem? Please describe.
When using libf3d and an external window you will need to use yaw, azimuth, elevation to move but to get them in degree you would need to calculate them from the camera position.

Describe the solution you'd like
It could be useful to have getters for these parameters. I know they are not actually parameters, but ways to manipulate the camera, but a getter for yaw/elevation that returns the angle of the camera to the model can be useful, also distance from the model etc.

Contribution
I'm sorry, I don't know C++

[mwestphal]

but a getter for yaw/elevation that returns the angle of the camera to the model can be useful

I suppose they could be computed for easier usage of the class indeed.

distance from the model etc.

This one is way more complex, unless you mean distance to the focal point.

[Nokse22]

This one is way more complex, unless you mean distance to the focal point.

Yes, from the focal point.