headers: added direct_to_mx, rearranged UA

direct_to_mx: added check for hop count when not authenticated
headers: added reject option to .ini
headers: refresh config once per connection

declare config.main.reject as boolean
added from_matches results
renamed from_matches -> from_match
headers: updated for net_utils syntax
data.headers: renamed hook_data to refresh_config

because that's all that function does
headers: added tests
headers: added rudimentary MLM detection
headers: added checks & rejects sections to config

so that each header test can be individually enabled/disabled, and rejections for each test can be too.
headers: updated docs with new methods, check & reject

settings.
headers: ezmlm detect with match (was end)
headers: added config defaults