Add convenience methods for annotations, shapes, and images

[jonmmease]

Overview

This PR adds a set of new convenience methods for annotations, shapes, and images

• fig.add_*
• fig.select_*
• fig.for_each_*
• fig.update_*

Where * is annotation(s), shape(s), or image(s).

cc @nicolaskruchten

[nicolaskruchten]

Possible issue: we’re going to have an ‘image’ trace type before long so there would be a conflict around add_image... should we use add_layout_image?

[jonmmease]

Oh, good point. Thanks for catching that! I'm fine with add_layout_image/select_layout_images/etc. Should we do the same for shapes and annotations or treat image as a special case?

[nicolaskruchten]

Tough call but I think special case for image makes the most sense to me. There isn’t and likely won’t be a non-layout annotation or shape...

[jonmmease]

Renamed in fd0ae43

[nicolaskruchten]

Looks good, let's merge it and I'll QA the whole thing this afternoon? 💃