DATAREDIS-330 - Add support for SENTINEL commands.

add support for commands:
  SENTINEL FAILOVER master
  SENTINEL SLAVES master
  SENTINEL REMOVE name
  SENTINEL MONITOR name ip port quorum

Original pull request: #92.

docs/src/reference/docbook/reference/redis.xml

@@ -222,6 +222,8 @@ public RedisConnectionFactory jedisConnectionFactory() {
   return new JedisConnectionFactory(sentinelConfig);
 }       
       ]]></programlisting>
+      <para>Sometimes direct interaction with the one of the Sentinels is required. Using <classname>RedisConnectionFactory.getSentinelConnection()</classname> or 
+      <classname>RedisConnection.getSentinelCommands()</classname> gives you access to the first active Sentinel configured.</para>
     </section>
     
     <section id="redis:template">