Normalize call to smtpd model
Add header for counting only

* Adds X-SMTPbin-Policy header -- 'write' for save, 'count' for stats only
Add index changes with info on policy
Fix tests and default policy
Add policy header and write, count policies, refs #6

* Add X-SMTPbin-Policy header
* Add 'write' policy to save message (default)
* Add 'count' policy to add to stats only