Logstash 5.0 doc fixes

[acchen97]

5.0 beta1

• Replace bin/plugin with bin/logstash-plugin
• Kafka comp matrix updates Updates to Kafka compatibility matrix #5645
• Monitoring API updates Monitoring API enhancements/cleanups for 5.0 #5732
• Bring settings file docs to config options parity - https://www.elastic.co/guide/en/logstash/master/logstash-settings-file.html
• Add messaging in command line flags page to encourage use of settings file instead

5.0 GA

• Delineation of Elastic vs Community supported plugins
• (added to 5.2 backlog) Getting started guide - add jdbc and http input examples, ES + S3 outputs, incremental building of a config file (showcasing auto-reload option)
• 5.0 Upgrades - upgrade guide for 2.0 and 2.2 should be consolidated into an overarching upgrades section
• Plugin specific doc additions:
  • Plugin version
  • Logstash core version compatibility, i.e. Logstash 2.4 - 5.x
  • (added to 5.2 backlog) Two links for plugin version navigation: master and latest compatible verison
  • Version release date
  • Link to change log
  • (added to 5.2 backlog) Add plugin code example snippet for most popular plugins - Alvin to define list
• Github page
  • (added to 5.2 backlog) Update top description of each plugin page
  • (added to 5.2 backlog) Add first [few] paragraphs plugin summary from documentation at top of README, also include official plugin docs link (master version)

Completed

• Community maintainer guide needs to be back to one page
• Add a glossary of terms
• Additional metrics for monitoring API - More metrics for monitoring API #4923
  • Better document/link http host & port info/settings from monitoring API page - Logstash 5.0.0-alpha2 - Host & port settings for monitoring APIs not documented #5285
• Settings file for config options - Use a settings file to complement command line argument parsing #4401
• Getting started guide updates
• Pipeline changes, messaging against tuning output workers
• Env variable page updates - funky rendering

Backlog

• (added to 5.2 backlog) New section "Adding & Collecting New Plugin Metrics" - adding guidance on how to add metrics to collect in plugins along with new metrics style guide Style guide practices when adding metrics to logstash plugins #5716
• (added to 5.2 backlog) New windows doc page - just under the install scope
• (added to 5.2 backlog) Deploying/scaling guide updates

[dedemorton]

Added glossary in PR #5237

[acchen97]

I just noticed the command line flags page could be formatted a bit better. Maybe something to update when working in the settings config file changes. :)

[dedemorton]

Metrics doc (currently early draft) are here: #5308

[dedemorton]

The link that points to the host/port commands was added in this PR: #5316

[dedemorton]

Closing this and moving backlog items to #6501 for tracking in 5.2.