when sorting files by category other than the name, and the data in that category is the same for both files, sort by the name instead
fix sorting by size

1)If the files have identical size, type or modification time, sort them by name for consistency - this fixes "random" sorting
2)Explicitly handle sorting by size (previously done by size_t->string, resulting in wrong sorting)
3)When sorting by size, put folders on top of the list and sort them by the number of child items
4)Introduce three-level fallback for file name comparison, as done in Dolphin. Thanks goes to Peter Penz


FIXED-IN:4.8.1

REVIEW:103895