Raphael Rosch authored Oct 20, 2020 and Stefano Crocco committed Oct 20, 2020

This fixes a couple issues, adds session persistence,
 creates a context menu option to restore deleted default buttons,
 and adds the ability to store the last used button to the OpenViews
 so it opens that automatically the next time the session is opened
 (but really, this needs to be moved to the session file).