isolate gems into build/dependencies, do not use any system gems
[rabbitmq] Use Bunny 1.5.0+

Fixes #1894
Add option to use a local jruby version instead of the vendored one

If we want to test against custom Jruby versions we need to ensure we use the correct jruby binary
Like what we can do with USE_RUBY=1 ./bin/logstash to use the local ruby binary we can do the same with the rake bootstrap job

Use ruby instead of jruby as binary in case we try out something else then jruby

Fixing a few issues with the build process

- Fix a very very very weird issue where the Gem::LoadError was being passed down
- Adhere to the USE_RUBY=1 logic to use the local ruby binary

Use if instead unless

Move require's to top of the file to avoid issues
TCP input host field contains source port

Fixes LOGSTASH-1849
https://logstash.jira.com/browse/LOGSTASH-1849

Fixes #1649
use Open3.popen3 to fix hanging IO in JRuby 9k
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
blocking test
Small refactoring of the file output class and adding a few tests to
cover edges cases..
Added more tests cases for encoding check
Wrapper for bin/logstash plugin