A handy function to set AST overlay in black color for publication #118
Description
Mostly image plots for publication (journal specifically) have labels, coordinate axes/grid, and title, etc in black color and with a white background. The GUI is with a blue color so with the current API we would need to call a set of functions to set the black color. It would be handy if we can have a wrapper to do this in just one function call.
We may also consider to have another mode with white AST overlay and a black background.
We may call this function as session.set_publication_theme()