Meta Issue: Logstash JDBC Integration plugin

[robbavey]

Required before inclusion in Logstash release:

• [x] Create logstash integration github repo
• [x] Integrate git repos
• [x] Remove duplicates
• [x] Ensure project builds and can create gem, integrate gemspec and gradle files
• [x] Update version to be 1 version greater than highest version of existing plugins
• [x] Restrict gemspec to only work Logstash >= 6.5
• [x] Fix unit tests
• [x] Fix integration tests
• [x] Create new changelog
• [x] Organize docs in correct structure(reviewed by @karenzone in #9)
• [x] Create proper doc index page (https://github.com/logstash-plugins/logstash-integration-jdbc/pull/9)
• [x] Publish integration plugin
• [x] Ensure docs build correctly
• [x] Replace references to individual plugins with integration plugin main repo (https://github.com/elastic/logstash/pull/11406)
• [x] Include integration plugin docs in main doc build(https://github.com/elastic/logstash-docs/pull/813)
• [x] Ensure that integration plugin docs do not overwrite regular docs for previous releases (https://github.com/elastic/docs-tools/pull/40)
• [x] Manually install and test integration plugins with existing releases:
  • [x] Test clean installation
  • [x] Test installation replaces old individual plugins
  • [x] Test jdbc input functionality
  • [x] Test jdbc static functionality
  • [x] Test jdbc streaming functionality

Other tasks

• [x] Migrate existing/close (and refer to new repo) existing issues and pull requests
• [ ] Refactor code to improve reuse across plugins - see (#5)
• [x] Ensure that integration plugin is kept up to date with changes in individual repos since initial merge.
  • [x] https://github.com/logstash-plugins/logstash-filter-jdbc_static/pull/53 - (#7)
• [ ] Update docs, README.md and other files in individual repos

[karenzone]

@karenzone Note to self: Flesh out docs requirements and work with @robbavey to turn this into a template (as we've discussed).