Add margin to the icons in the "List" view

[Palollo]

Now fixed to just 1 pixel to avoid icons touching each other,
but it can be made configurable in the future.

[derceg]

Hi @Palollo, could you add some information about why this is needed? Screenshots showing the problem and how this fixes it might be useful. Thanks.

[Palollo]

Hi, it is a subtle change, but makes the difference ;)
Before (it looks slovenly, the icons of files/folders are touching each other and the border of the window, there is no division or break between them):

After (looks nicer, clean, seemly, with just 1 pixel of margin, but it can be increased or even configurable by the user):

[derceg]

The general idea here could work, but the implementation, as it exists right now, isn't workable. The list of icons needed isn't static, since items can be added to the directory after the navigation has completed. Trying to retrieve a list of all necessary icons up front isn't going to work for that reason.

This would have to work something more like thumbnails view, where the images are generated on-demand and the image list is destroyed whenever the view changes or a navigation occurs.

[Palollo]

OK, indeed I reverted in my fork because it adds some lag in navigation.
I will improve it with the on-demand generation of images if I have some time some day ;)