Add ChangeLog entry and man page entry.

changes/enhancement1819

@@ -0,0 +1,4 @@
+  o Minor features:
+    - Relays that set "ConnDirectionStatistics 1" write statistics on the
+      birectional use of connections to disk every 24 hours.
+

doc/tor.1.txt

@@ -1027,6 +1027,10 @@ is non-zero):
     When this option is enabled, Tor writes statistics on the number of relayed
     bytes and opened stream per exit port to disk every 24 hours. (Default: 0)
 
+**ConnDirectionStats** **0**|**1**::
+    When this option is enabled, Tor writes statistics on the bidirectional use
+    of connections to disk every 24 hours. (Default: 0)
+
 **ExtraInfoStatistics** **0**|**1**::
     When this option is enabled, Tor includes previously gathered statistics in
     its extra-info documents that it uploads to the directory authorities.