swap_author_names revised to eliminate trailing comma and split/swap at first comma or space

[Starson17]

swap_author_names function previously split and swapped at the last space in the name, leaving a comma at the end of the author's last name when in "lastname, firstname" format and using the middle name as the last name when in "lastname, middlename firstname" format. This proposed change now splits at the first comma if there is a comma in the author name (when swap author name checkbox is selected) or at the first space in the name when no comma is found.

Tested on Windows Vista only

[Starson17]

bazaar changes file

[kovidgoyal]

Fixed in branch trunk. The fix will be in the next release.