Minor edits (#2380)

* Added a shortcut for remove_all_except() in scene_embed

* Added **kwargs argument to get_axis_label() and get_axis_labels() such that properties of the label like font size and t2c can be configured.

* Comments for set_color_by_rgba_func and set_color_by_rgb_func were ambiguous; clarified the comments.

* Changed the comment to remove the old description. The old description was valid up until pull request #2316.