Adds a table with the exhaustive list of all available headers with a brief description (mostly from `org.elasticsearch.rest.action.cat.RestNodesAction`) so that people do not need to go searching for them in the code like I did, or search through `nodes?help`.
If we want to have a full picture of versions running in a cluster, we need to add a `_cat/plugins` endpoint.
Response could look like:
```sh
% curl es2:9200/_cat/plugins?v
node component version type url desc
es1 mapper-attachments 1.7.0 j Adds the attachment type allowing to parse difference attachment formats
es1 lang-javascript 1.4.0 j JavaScript plugin allowing to add javascript scripting support
es1 analysis-smartcn 1.9.0 j Smart Chinese analysis support
es1 marvel 1.1.0 j/s http://localhost:9200/_plugins/marvel Elasticsearch Management & Monitoring
es1 kopf 0.5.3 s http://localhost:9200/_plugins/kopf kopf - simple web administration tool for ElasticSearch
es2 mapper-attachments 2.0.0.RC1 j Adds the attachment type allowing to parse difference attachment formats
es2 lang-javascript 2.0.0.RC1 j JavaScript plugin allowing to add javascript scripting support
es2 analysis-smartcn 2.0.0.RC1 j Smart Chinese analysis support
```
Closes#4824.
By default active, rejected and queue thread statistics are included for the index, bulk and search thread pool.
Other thread statistics of other thread pools can be included via the `h` query string parameter.
Closes#4907
- Removed "ok": true from response examples
- Added "created" flag to index response examples
- Replaced exists flag with found in delete response examples
Chris Earle
David Pilato
Luca Cavanna
Martijn van Groningen
Alexander Reelsen
Andrew Raines
Clinton Gormley