add Authentication-Results header (RFC 5451)
Auth-Res: added SPF results
auth: added auth method to A-R header
lookup_rdns: added iprev to Auth-Results header
connection: store auth results in transaction

when a transaction is available. Else, default to connection
move old Auth-Results to Original-Auth-Results
If host is allowed by acl, don't deny the recipient because the domain isn't in the allow list
spf: moved auth_results processing out of switch

so that it's always added to auth_results
previously, when SPF failed, it wasn't added.
When combined with a delay_deny plugin, the connection would ultimately pass without SPF results saved
connection: made code more linear

make it easier to read and grok
import Steve's p0f plugin
my first whack at p0f

renamed p0f -> connect.p0f  (as other plugins do)
whitespace/indention cleanups
added config option for adding the X-Haraka-p0f header (enable/disable/rename)
refactored several methods to remove unnecessary indentions
changed passing of 'this' in log* methods to (var plugin = this) and passing plugin, so log entries have the correct plugin name (no, I don't know why that fixes it)
consolidated 3 instances of repetition into format_results function
added a couple function names to anonymous functions (useful debug info)
p0f: added docs
TODO: added plugin renames
TODO: added rename attachment -> data.attachment
TODO: added rename toobusy -> connect.toobusy
Merge pull request #412 from msimerson/p0f-smf

P0f smf
Merge pull request #413 from msimerson/headers

headers: fixed Date header bug
Merge pull request #410 from smfreegard/master

If host is allowed by acl, don't deny the recipient because the domain isn't in the allow list
Merge pull request #409 from msimerson/authentication-results-rfc5451

add Authentication-Results header (RFC 5451)
Merge pull request #411 from msimerson/todo

Todo