Implement custom console classes

[Anthony-B-Russo10]

Going off of what grionde said on the forums, there needs to be a way to save the Celestia log so problems with catalog files can be found. Specifically as a basic TXT file.

grionde's original post: https://celestia.space/forum/viewtopic.php?f=15&t=20315

[375gnu]

I see this as a custom console class instead of build-in one. A new console should be able to display log entries in GUI dialog, save them to file and so on.

[pirogronian]

And using command line options would be very useful in case GUI is unavaliable (crash or so).

[375gnu]

#908 implements the original idea.