doc: Add defaults for some transport options

doc/tor.1.txt

@@ -295,27 +295,28 @@ GENERAL OPTIONS
     client launches the pluggable transport proxy executable in
     __path-to-binary__ using __options__ as its command-line options, and
     forwards its traffic to it. It's the duty of that proxy to properly forward
-    the traffic to the bridge.
+    the traffic to the bridge. (Default: none)
 
 [[ServerTransportPlugin]] **ServerTransportPlugin** __transport__ exec __path-to-binary__ [options]::
     The Tor relay launches the pluggable transport proxy in __path-to-binary__
     using __options__ as its command-line options, and expects to receive
-    proxied client traffic from it.
+    proxied client traffic from it. (Default: none)
 
 [[ServerTransportListenAddr]] **ServerTransportListenAddr** __transport__ __IP__:__PORT__::
     When this option is set, Tor will suggest __IP__:__PORT__ as the
     listening address of any pluggable transport proxy that tries to
     launch __transport__. (IPv4 addresses should written as-is; IPv6
-    addresses should be wrapped in square brackets.)
+    addresses should be wrapped in square brackets.) (Default: none)
 
 [[ServerTransportOptions]] **ServerTransportOptions** __transport__ __k=v__ __k=v__ ...::
     When this option is set, Tor will pass the __k=v__ parameters to
     any pluggable transport proxy that tries to launch __transport__. +
-    (Example: ServerTransportOptions obfs45 shared-secret=bridgepasswd cache=/var/lib/tor/cache)
+    (Example: ServerTransportOptions obfs45 shared-secret=bridgepasswd cache=/var/lib/tor/cache) (Default: none)
 
 [[ExtORPort]] **ExtORPort** \['address':]__port__|**auto**::
     Open this port to listen for Extended ORPort connections from your
-    pluggable transports.
+    pluggable transports. +
+    (Default: **DataDirectory**/extended_orport_auth_cookie)
 
 [[ExtORPortCookieAuthFile]] **ExtORPortCookieAuthFile** __Path__::
     If set, this option overrides the default location and file name