Plugin.pm: made is_naughty is now a getter too
log/summarize: set undefined strings as empty str

avoids undef warnings
dmarc integrated with Mail::DMARC

reimplemented dmarc module to use Mail::DMARC
updated SPF plugin to save SPF results in dmarc_spf note
update dkim to store DKIM results in dkim_result & dkim_verifier notes
added dmarc (run SPF & DKIM) first comment
dspam: remove hard coded default in train_ methods
headers: added POD descripting each header
geoip: added named array for invalid args

so it passes Perl::Critic tests