WS cleanups
headers: added has_invalid_header

renamed some camelCase methods
refactored a couple blocks into functions
moved config checking/loading into functions where used
headers: strip Return-Path header in incoming mail

read the comments. It's complicated.
headers: refactored each function into a data_post hook
Merge pull request #425 from msimerson/headers

Changes committed - thanks Matt.  Looks much better now.

BTW - when you fix up something we've commented on and you then think it's ready - can you make another comment on the request to that effect as Github doesn't send notifications when you add additional commits and it means that I'll notice quicker ;-)