Initial commit for creating plugin documentation into asciidoc

Fixes #1741
Add Plugin docs in ascii format

Fixes #1741
[DOCS] Add index page generation for each plugin type

Fixes #1741
Minor doc fixes

Fixes #1741
Fix for default codec. Based on PR #1829

Fixes #1741
Some documentation generation fixes

- Add docgen command to use internal libraries
- Fix loading of base files due to plugin path changes
- Fix loading of jar dependency files
- Remove kramdown gem and actions
- Cleanup the generated synopsis a bit

Fixes #2009