Update Rule Editor/Creator for larger "Rule Source" window

## What?
Currently on Editing or Creating a rule, you get a very small window you can drag and expand open to make it larger. It would be user friendly if we can make the Rule Source box larger (Auto Expand to the whole page) or most of the space outside the Reference.

If we could get the Reference section as a pop-out like the side menu, or an option to hide it, would also give more space for editing rules.

## Why?
Create a more useful environment to edit and create rules. Being able to see more of the rule in the editor, would help with development.

## Your Environment

* Graylog Version: 3.3.1