Add --data-directory-config option to "repmgr node check"

Implements part of GitHub #523.

doc/repmgr-node-check.sgml

@@ -86,6 +86,16 @@
       </simpara>
      </listitem>
 
+     <listitem>
+      <simpara>
+        <literal>--data-directory-config</literal>: checks the data directory configured in
+        <filename>repmgr.conf</filename> matches the actual data directory.
+        This check is not directly related to replication, but is useful to verify &repmgr;
+        is correctly configured.
+      </simpara>
+     </listitem>
+
+
     </itemizedlist>
   </para>
   </refsect1>
@@ -105,6 +115,7 @@
         <listitem>
           <simpara>
             <literal>--nagios</literal>: generate output in a Nagios-compatible format
+            (for individual checks only)
           </simpara>
         </listitem>
       </itemizedlist>