FKED-89: Add support for deleting scenes from open experience 🖼💥

[techninja]

FKED-89: As a user I'd like to delete scenes

Based on #35, so merge that first.

This PR does the following:

• Adds a new button for the scene card component (plus associated api, action, and reducer methods), allowing for complete deletion of scenes via the API and in the UI

To Review:

• Checkout this branch, run yarn start, and login with your credentials.
• Create a test experience, and at least 3 test scenes.
• See that delete buttons (with 🗑 icons) appear on the scene cards
• Click the "Delete" button on a scene that is not being edited
• See that you're presented with a modal confirmation dialog
• Click "Cancel" and verify that nothing happens
• Click the delete again, and the click confirm
• See that the scene card disappears, and on page refresh the scene is gone.
• Click to edit a scene (if one isn't open).
• Click the delete button on that scene (the card should have a green outline)
• See that the scene edit unloads after deletion and you can continue editing