* [ILM] Add documentation for error handling in ILM
This adds some initial documentation for error handling and retrying failed
steps for index lifecycle management
* [DOCS] ILM API Ref edits
* [DOCS] Fixed endpoint for DELETE policy.
* [DOCS] Removed comparison to setting index.lifecycle.name to null.
* [DOCS] Fixed xrefs to explain API.
debadair
Tal Levy
Lee Hinman