Logstash 5.6.x doc changes

[dedemorton]

5.6.x

• Update Kafka compat matrix. See Alvin's comment below.

5.6

• Doc page for Logstash modules and how they work
• Docs for netflow and arcsight modules need to be ported to 5.6
• Lots of other stuff that didn't appear on this list. :-P

Soon after 5.5

• Update docs about running Filebeat Modules. Include docs for new modules. Make sure the steps are still correct and that the syslog example works. Run tool to update configs. See Logstash docs and configs for Filebeat modules #6542
• Add DLQ policy section to Elasticsearch output docs (can add this after 5.5 releases). See Document DLQ behavior in ES output logstash-plugins/logstash-output-elasticsearch#617.
• Document how to limit DLQ disk usage. See Add documentation for DLQ max bytes #7658
• Get the plugin docs building in master.
• Add links to DLQ plugin when the docs are building (need to wait until DLQ plugin docs are available in master and 5.x branches)

Moved backlog to #6963

[acchen97]

Just noting down here to include updating the Kafka plugin compatibility matrices through Kafka v0.11 for LS 5.6:

• Update compatibility table to include latest plugin version releases logstash-plugins/logstash-input-kafka#214
• Update compatibility table to include latest plugin version releases logstash-plugins/logstash-output-kafka#142

[dedemorton]

Changing label to close out this PR since 5.6 has shipped.

[dedemorton]

@acchen97 Speaking of the Kafka matrix. Where are we at with that? Can I close the open item here and move it to another issue? Or close it completely?

[dedemorton]

Never closed this out, so I'm doing it now.

[acchen97]

@jordansissel is tracking and handling the Kafka matrix enhancement. Thanks for closing this.