Visualize a slide with annotation, tiles and label

[luzuku]

The slide class needs a method to visualize itself at the lowest resolution possible, like a thumbnail. This method should also be able to optionally lay over the annotation, the current tiles/regions and a single label. Multiple labels will not be supported as one can simply save the thumbnail multiple times with different labels.

Ideally this should work in two ways:

1. Save as an image when a path is given
2. Show inside a notebook without saving