Describe the feature:
Allow the user to debug / dry test scripted fields by playing input document from a selected filter into the painless script on the screen and showing the outcome on the script rather than modifying the data in the index.
Suggested GUI:

1. Search / select index pattern
2. type your painless script
3. Use play button to play the document into the script
4. Allow the user to play next / prev document by adding next prev buttons
5. Show the scripted field output in the document [highlighted]
   Describe a specific use case for the feature:
   As a developer / user I want to add scripted fields to every document I ingest in my index / index template. I need an easy tool to allow my to test my script without contaminating the data itself