Add a link "request help" that enables to apply a form describing what we ask for

A link "Request for help" appears in the header. It makes a popup appear with:

• A text: "Use this form to require some help on using Studio: you can ask for some very targeted and technical questions or explain more generaly what you would like to achieve, we will get back to you".

• A texta area (wide enough)

• A submit button

• A cancel button