Feature request - specify output fields when quering ES

Hello,

First of all, thank for you great application. It helps me everyday working with ES:) I'm working with Mirage in chrome(as an extension). I can modify query manually, bet every change in gui, resets my changes to output fields (e.g."_source": ["user", "message", ...] according to this post https://stackoverflow.com/a/9605566/1615070 )

Is there possibility to add in Mirage button with "output" where I can define which fields should be returned by ES?

Start in the Mirage Chrome extension's query GUI and trace how GUI changes rebuild the Elasticsearch request. Add a user-controlled output-fields option that survives GUI edits and verify that requests return only the selected fields.

Written by the indexing model from the issue text.