Allow for full editing of the QE input

Hello,

In the Step 2: submit work chain when in Expert mode, I think the "Advanced settings" should give full access to the QE input file.

The user could click on a button and see & edit the QE input file.

Then that modified input is submitted.

I think it is very important (you can have a Warning saying "modify at your own risk, calculation might crash").
Certainly for expert users but even for non-expert in order to learn.
In addition if a non-expert ask for questions and someone tell them that they should change X input variable, then they can do it easily.

I would consider this an important feature to add flexibility.

-- Sam