Add reset camera button

[BBortfeldt]

There is no option to reset the camera to the default position and target.

It is possible to do this by centering the camera to the table or the center machine but this should only be a workaround and a clear UI entry to do this would be a better solution.
There should be a toolbar at the top of the screen which can contain buttons. The button to reset the camera position should be added there.

The main problem of the implementation should be to find a fitting icon and implement the toolbar. Code to reset the camera is already available and is used to reset the camera at startup.