calibredb sort on multiple fields

[Raphaël Droz]

`calibredb list --sort-by=author_sort,series,series_index --fields=title,authors,series,series_index`

Expected:
Sort based on Author, then series' name, then series' index

Actual:
Unknown sort field: author_sort,series,series_index

(When multiple books of an author exist, `--sort-by=author_sort` output them randomly ordered)

[Kovid Goyal (kovid)]

Fixed in branch master. The fix will be in the next release. calibre is usually released every alternate Friday.

 status fixreleased