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