Add Transparent Proxy and PROXY v2 support and help page

examples/patchbay.conf.client

@@ -12,4 +12,8 @@ TargetPort = 2222
 # The target's host key is trusted on first connect and pinned here.
 # KnownHosts = /etc/patchbay/known_hosts
 # ServicesInterval = 30
+
+# Transparent source spoofing: routing table (and rule priority) patchbayd uses
+# to route replies from loopback services back to itself. 0 = set it up by hand.
+# TransparentTable = 470
 # LogLevel = info