ISPN-4363 Add documentation for Cluster Listeners

* Added documentation about cluster listeners
* Added documentation about filters
* Added documentation about retry

https://issues.jboss.org/browse/ISPN-4363
question1: the ```Converter``` can only be used with ```KeyValueFilter```?
question2: can the ```Converter``` only convert the values? can't be used to convert the keys and values to another format? 
comment: monospace for ```KeyValueFilter```