AlbumArtistSort and ArtistSort - switch first and last names

I had a look at the expression used in #17 and it seems to me that an escape of the opening bracket in the first match group is missing. A correct expression would be

^([^,\[]+)\s([^,\[]+)$

The same applies to the expression using in #18

^([^,\[]+)\s([^,\[]+)\s(\[.+\])$