Mass convert

[Goddard]

I've added the ability to mass-convert MOS types.

[Goddard]

I've not checked code in the IDE yet. As I see you mostly move large amounts of code to another place. Unfortunately, GitHub interface don't allow to notice that clearly. I recommend in this case make special commits that just moves existing code with minimal and absolutely necessary changes to facilitate reviewers work. So, can you rebase your changes to follow that suggestion?

You change a GUI in this PR. Can you attach a screenshot or two (before/after) with the notable differences highlighted?

Here is the GUI before removing the close checkbox. I made this video awhile ago. https://www.youtube.com/watch?v=jd3RItOyFxU

[Goddard]

Think I addressed many issues.

[Argent77]

Nice work!

However, I've noticed a couple of issues that should be fixed.

1. It looks like you based the changes on Version 2.1-20200620 which is over a year (and 200 commits) behind the current state and causes a couple of merge conflicts. Please fetch the latest changes from upstream to resolve them.
2. The input file dialog of both MOS converter tabs currently selects the Documents folder of the system by default. Please change it so that the game's root folder is selected instead. Moreover, the file selection dialog should remember the last selected folder.
3. There is a layout issue if you select a number of input files and resize the dialog window afterwards. I was able to trigger it when the input list contained enough entries to show a vertical scroll bar.
4. There is currently no way to remove selected input files from the MOS converter dialog, even after closing and reopening the dialog. Input should also be cleared after the conversion is done. Please add this functionality. (Take a look at the BMP converter how it can be done.)

And more of an aesthetic issue, the content of the "PVRZ-based" tab would probably look better if it were aligned at the top.

[Goddard]

I think we are in a good spot now. Let me know what you think.

[Argent77]

It works nicely now!

I'd like to make three more suggestions though:

1. Show more feedback if the conversion cannot be performed for some reason. For example, skip input files with a message if they cannot be read.
2. If the user unchecked "Close dialog after conversion": Show a notification when the conversion process is complete because this is difficult to see when you convert a great number of files at once.
3. If the user unchecked "Close dialog after conversion": Clear the content of the input and output list controls when the operation is complete. It's more intuitive than manually closing and reopening the converter to clear the list.