Tor support

- Add support for using Tor via a socks5 proxy.
- Tor usage of the milter and the updater process are configured
  separately.
- Restructure the config file and add some documentation.

config/config.toml

@@ -1,17 +1,60 @@
 #
 # Husk config file
 #
-connection = "localhost:3000"
 
+# The directory for anything Sequoia PGP related (keystore, certstore).
+# 
+# default: /var/lib/husk
 sequoia_home = "/tmp/sq_home"
 
-#keyservers = [ "hkps://keys.openpgp.org/", "hkps://mail-api.proton.me", "hkps://keys.mailvelope.com", "hkps://keyserver.ubuntu.com", "hkps://sks.pod01.fleetstreetops.com" ]
+[milter]
+# IP and port the milter will listen on.
+#
+# no default, must be specified.
+connection = "localhost:3000"
+
+# Keyservers to use for key lookup.
+#
+# Example:
+# keyservers = [ "hkps://keys.openpgp.org/", "hkps://mail-api.proton.me", "hkps://keys.mailvelope.com", "hkps://keyserver.ubuntu.com", "hkps://sks.pod01.fleetstreetops.com" ]
+#
+# The default is the empty list, which prevents keyserver lookups.
 keyservers = [ "hkp://example.com" ]
 
+# Location of the pid file of the milter.
+#
+# default: /var/lib/husk/husk.pid
+
+# Subject header lines are protected (exchanged).
+#
+# Specify your replacement string:
+# subject_replacement = "Encrypted message"
+#
+# default: "..."
+
+# Tor usage: If configured, the milter will use Tor via the specified
+# sock5 proxy.
+#
+# use_tor_via = "socks5://localhost:9050/"
+#
+# default: unconfigured, meaning: no usage of Tor.
+
 [updater]
+
+# The interval between two update requests for a certificate are
+# random. 
+#
+# wait_min and wait_max specify the range for that randomness.
+# defaults:
+# min_wait = 5
+# max_wait = 3600
 wait_min = 1
 wait_max = 2
 
+# Tor usage of the updater process. Semantics (and default) are the same 
+# as with the milter.
+use_tor_via = "socks5://localhost:9050/"
+
 [logging.appenders.console]
 kind = "console"
 [logging.appenders.console.encoder]