Custom HTML/JS on page

As an Admin I'd like to be able to put any JS/HTML I want on top and in the bottom of pages so that I'm able to post adds/counters there

Acceptance Tests:

• Given I'm in Admin mode, I can see buttons "Add Custom HTML/JS" in each highlighted box (see attached)
• Given I've added HTML/JS, it is displayed on each page (including admin pages).
• Given I've opened editing form, I have Cancel and Save buttons.

Criteria on labels:

• If banner is empty, then button on page should be labeled with 'Add Custom HTML/JS'
• If banner is not empty, then button on page should be labeled with 'Edit Custom HTML/JS'
• In modal dialog for banner uploading there is always Save and Cancel buttons, they don't change labels.
• Dialog title: Paste your HTML/JavaScript here: