working on listen-based wiki notifications:

1) When storing the message in the archive, validate the x-opencore headers.  If validation fails, remove all x-opencore headers.  If validation succeeds, remove the validation key header.  If validation succeeds, replace the From: header with the value of the x-opencore-send-from header.

2) When sending the message, validate the x-opencore headers.  If validation fails, remove all x-opencore headers.  If validation succeeds, remove the validation key header.  If validation succeeds, replace the From: header with the value of the x-opencore-send-from header.  If validation succeeds, do not send the message to any addresses listed in the x-opencore-do-not-send-to header.  If validation succeeds, remove all x-opencore headers.

3) When checking whether the policy returns POST_ALLOWED for the message, validate the x-opencore headers.  If validation fails, do nothing out of the ordinary.  If validation succeeds, return POST_ALLOWED.

All of this stuff should be refactored into overrides in opencore somehow, hopefully.
remove the header validator implementation
fix typos