[ENHANCEMENT] A second, separate icon orientation setting for desktop's default icons (home, file system, trash, removable devices)

Brought up within issue #305 (closed) is the idea of having a second, separate icon orientation setting for desktop's default icons (home, file system, trash, removable devices).

The main thing is related to removable devices since they'll populate the desktop, but that can result in them being placed in-between and/or amongst your various desktop icons and such because Xfce does not differentiate between the default icons and icons for everything else like photos, videos, text files, etc.

While it can still make sense for the likes of home, file system, and trash but, since those would not disappear and reappear like removable devices would, the fix that was implemented for #305 (closed) should generally already mostly take care of that as long as the user knows to manually move the corresponding icons to a different location on their screen.

...that being said, if dealing with a situation that involves changing monitors with different resolutions or the like, then I suppose even the fix for #305 (closed) may not be enough, such as if you have your icon orientation on the left vertically but have manually moved your default icons onto the right side, or you have your icon orientation on the top horizontally but manually moved your default icons to the bottom. That is, if you had manually set their positions on a smaller screen but switch to a larger one (such as the situations of connecting a laptop to a larger desktop-size monitor), then those manually-placed default icons will no longer be on the edge.