Fix and clean up CDC documentation

The CDC_users.md document was not linked to and was in the wrong place. It
should reside in the protocol directory since it relates to the CDC protocol.

Documentation/Reference/CDC_users.md

@@ -1,45 +0,0 @@
-#Change Data Capture users
-
-CDC is a the new MaxScale protocol that allows compatible clients to authenticate and
-register for Change Data Capture events.
-The new protocol must be use in
-conjunction with AVRO router which currently converts MySQL binlog events into
-AVRO records.
-
-
-Clients connect to CDC listener and try authentication using credentials such as username and password.
-
-Users could be created by adding an entry into the 'cdcusers' file that should be available in /$datadir/$service_name/
-
-Example file location is:```/var/lib/maxscale/CDC_service/cdcusers```
-
-**Note**: If no users are found in that file or if it doesn't exist, the only available user will be the ```service user```, if specified in service section:
-
-###The Avro conversion service
-```
-[avro-service]
-type=service
-router=avrorouter
-source=replication-service
-## default service user
-#user=cdc_user
-#password=cdc_password
-```
-
-###How to create CDC users
-
-```
-bash$ cdc_users [-h] USER PASSWORD
-```
-
-The output of this command should be appended to ```/var/lib/maxscale/<service
-name>/cdcusers```
-
-```
-bash$ cdc_users user1 pass1 >> /var/lib/maxscale/avro-service/cdcusers
-```
-
-**Note:** New users will be loaded into MaxScale at the first authentication attempt.
-
-Users could be removed by deleting the related rows in 'cdcusers' file.
-