HAWQ-1553 Add option to hawq extract to specify log directory

Author: outofmem0ry

markdown/reference/cli/admin_utilities/hawqextract.html.md.erb

@@ -73,6 +73,9 @@ where:
 <dt>-\\\-version  </dt>
 <dd>Displays the version of this utility.</dd>
 
+<dt>-l, -\\\-logdir \<logfile\_directory\>  </dt>
+<dd>Specifies the directory that `hawq extract` uses for logs. The default is `~/hawqAdminLogs/`.</dd>
+
 **&lt;connection_options&gt;**
 
 <dt>-h &lt;host&gt;  </dt>