Media: Implement WIP advanced image settings dialog

[aduth]

Related: #307

This pull request seeks to implement a minimal set of behavior related to advanced image settings editing. Specifically, the changes included add a new TinyMCE toolbar button to be shown in the inline toolbar for images which, when clicked, toggles the display of a <Dialog /> component, currently rendered with dummy content.

Implementation notes:

I fully expect the structure of the Redux state and <EditorMediaAdvanced /> component to need extensive revisions as this functionality is built, thus the lack of proper documentation and testing. That said, feel free to comment on the proposed structure as-is.

Testing instructions:

Confirm that the included behavior is only shown in development environments by temporarily setting post-editor/media-advanced to false in config/development.json and restarting make run.

1. Navigate to the Calypso post editor
2. Select a site, if prompted
3. Insert an image to the post content
4. Click the image to select it
5. Note that...
   • If post-editor/media-advanced is true, an "Edit" icon is shown in the inline toolbar
   • If post-editor/media-advanced is false, an "Edit" icon is not shown in the inline toolbar and there are no errors in the developer tools console
6. Click the Edit button in the inline toolbar
7. Note that a dialog is shown with dummy content

[dmsnell]

why put these here when we are already using destructuring in the function declaration?

function EditorMediaAdvanced( { visible = false, toggleVisible = noop } ) {
    …
}

[aduth]

why put these here when we are already using destructuring in the function declaration?

You know, that's an interesting question. One has to wonder why defaultProps was one of the two properties that the React team chose to support for stateless functional components. Perhaps there's some semantics of defaultProps that wouldn't be reflected with the destructured default values? I couldn't find much discussion on the topic, though this commenter appears to prefer default arguments from a function purity perspective. On the flip-side, it does make the function declaration line a bit longer.

Do you have a strong preference either way? I'm inclined to keep it as is, mostly for aesthetics to this last point and for proximity to the propTypes declaration for quick scanning. Additionally, it may be that this is easier for static analysis if we choose to pursue some automated documentation of components.

[dmsnell]

Do you have a strong preference either way?

not at all 😄

[kellychoffman]

If post-editor/media-advanced is true, an "Edit" icon is shown in the inline toolbar

👍

If post-editor/media-advanced is false, an "Edit" icon is not shown in the inline toolbar and there are no errors in the developer tools console

👍