- Do deprecation checks *before* merging in the defaults. This keeps the
pipeline from foolishly warning users about deprecated settings simply
because those settings have default values.
- make plugin statuses milestones instead. (LOGSTASH-1137)
  The previous taxonomy confused users due to overloaded meanings of
  'beta' and 'experimental'.
- Switch to using milestone numbers instead of plugin status labels
(LOGSTASH-1137)
- Rename plugin-status doc to plugin-milestones