Deprecate mmmon and ndbclustermon

Separated mmmon and ndbclustermon from the list of supported modules into
their own legacy section. Added a warning about the deprecation to the
relevant documents.

Also added the csmon link to the documentation contents.

Documentation/Documentation-Contents.md

@@ -101,10 +101,14 @@ Common options for all monitor modules.
 
 Module specific documentation.
 
- - [Aurora Monitor](Monitors/Aurora-Monitor.md)
- - [Galera Monitor](Monitors/Galera-Monitor.md)
- - [Multi-Master Monitor](Monitors/MM-Monitor.md)
  - [MariaDB Monitor](Monitors/MariaDB-Monitor.md)
+ - [Galera Monitor](Monitors/Galera-Monitor.md)
+ - [ColumnStore Monitor](Monitors/ColumnStore-Monitor.md)
+ - [Aurora Monitor](Monitors/Aurora-Monitor.md)
+
+Legacy monitors that have been deprecated.
+
+ - [Multi-Master Monitor](Monitors/MM-Monitor.md)
  - [MySQL Cluster Monitor](Monitors/NDB-Cluster-Monitor.md)
 
 ## Protocols

Documentation/Monitors/MM-Monitor.md

@@ -1,5 +1,7 @@
 # Multi-Master Monitor
 
+**NOTE:** This module has been deprecated, do not use it.
+
 ## Overview
 
 The Multi-Master Monitor is a monitoring module for MaxScale that monitors Master-Master replication.

Documentation/Monitors/NDB-Cluster-Monitor.md

@@ -1,5 +1,7 @@
 # NDB Cluster Monitor
 
+**NOTE:** This module has been deprecated, do not use it.
+
 ## Overview
 
 The MySQL Cluster Monitor is a monitoring module for MaxScale that monitors a MySQL Cluster. It assigns a NDB status for the server if it is a part of a MySQL Cluster.

Documentation/Release-Notes/MaxScale-2.3.1-Release-Notes.md

@@ -16,6 +16,13 @@ Secondary masters can now be specified also when file + position
 based replication is used. Earlier it was possible only in conjunction
 with GTID based replication.
 
+### `mmmon` and `ndbclustermon`
+
+Both of these modules have been deprecated and will be removed in a future
+release. The functionality in `mmmon` has been largely obsoleted by the
+advancements in `mariadbmon`. The `ndbclustermon` is largely obsolete due to the
+fact that there are virtually no users who use it.
+
 ## New Features
 
 ### MaxCtrl