Beats Doc Updates for 5.3

[dedemorton]

5.3:

• Make sure these sections get edited:
  • Config reload (backlog. See Dynamic configuration reloading for modules in Metricbeat #3281)
  • Docs about -setup for loading dashboards (see Make -setup load the Beat dashboards #3506).
• Heartbeat docs: Add content about loading sample dashboards when the dashboards are available.
• Check cURL statements used in docs to make sure they include content-type when passing a body.
• Make these minor fixes to the getting started guides:
  • Mention that command line options aren’t available when using init.d script. See Command line options aren't available when using init.d script to start Beats #812 (also contains some info relevant to issue Simplify getting started guide(s) by showing how to run each beat in the foreground #1047)
  • Filebeat GS: move step about importing the index pattern in Filebeat into the doc for Filebeat rather than making users jump to the platform ref for a simple command.
• Fix bugs flagged for 5.3 plus:
  • Clarify Filebeat docs wrt the index setting (see Documentation on filebeat logstash-output is not clear for index setting #3558).
• Make sure our Beats developer guide is up-to-date and that the Metricbeat docs point to the docs about the single generator (we now have a single generator for generating either a Beat or a Beat based on Metricbeat--see Update generator to reference to the docs #3491). Make sure the blog post mentioned in the PR has been updated.

Follow up:

• See if we can remove close this issue: Add a separate topic to describe how events are handled when max_retries is exceeded #652

[dedemorton]

Closing this and moving the backlog #4021