One button should only add default applications or overwrite them, never remove #7
Description
Currently, the logic is to add or remove a mimetype's configured based entirely on whether it is in the selected list or not, entirely ignoring whether the application it is currently configuring is even in the list of possible options.
#6 somewhat fixes this by making it not overwrite other apps configs. However, it will still remove its own settings which is not desireable either I think.
It's also possible to add a second button to remove associations, and #6 makes this easy because we have a second list of which mimetypes an application should open by default. If implemented, it should show a warning that this doesn't prevent the application from opening the mimetype, just doesn't make it default behavior, and its better to find a different application that can open it. However, since that isn't very useful behavior, it seems to me like there would be no reason to add this.
Will be implemented in the same PR that I implement #5 in I think, since this change makes #5 easier to implement by simplifying branches the code can take.