Documentation: Configuration Format

At https://zookeeper.apache.org/doc/r3.6.2/zookeeperReconfig.html#ch_reconfig_format, an updated configuration format is introduced, in which client port is now specified as part of the server keyword specification.

There are two issues with the documentation:

• Elsewhere in the documentation, such as https://zookeeper.apache.org/doc/r3.6.2/zookeeperStarted.html and https://zookeeper.apache.org/doc/r3.6.2/zookeeperAdmin.html, the documentation still uses the old format. System administrators who did not read the Dynamic Reconfiguration page will miss this change.
• The Backwards Compatibility subsection is very easily missed when glancing through the https://zookeeper.apache.org/doc/r3.6.2/zookeeperReconfig.html#ch_reconfig_format. I think this might be the cause for CURATOR-526.