Media: Populate advanced editing with parsed media

[aduth]

Related: #307, #2085

This pull request seeks to further progress advanced image editing by parsing the selected media item and adding the necessary behavior to update markup in the post editor after the user has chosen to save their changes.

This is very much a work-in-progress. As of now, the only expected behaviors are:

• A user can edit a selected image from the inline toolbar
• A modal appears, displaying the media's ID and a save button
• Upon clicking Save, the image is replaced with the text "Updated"

Note that this feature is feature-flagged, and is only available in a development environment. You can/should verify that these options are unavailable in all other environments.

Implementation notes:

The advanced media modal is no longer rendered by the <PostEditor /> component, but instead by the media/advanced TinyMCE plugin. This is done so that the expected insertMedia prop handler can be passed to the modal which, when called, replaces the current selection with the passed markup.

Testing instructions:

1. Navigate to the Calypso post editor
2. Select a site, if prompted
3. Insert an image into the post contents
4. Select the image by clicking it
5. Click Edit in the inline toolbar
6. Note that a dialog is shown, containing the image's ID and a Save button
7. Click Save
8. Note that the modal is dismissed and that the image has been replaced in post contents with "Updated"

[dmsnell]

I think it works well when we use noop from lodash (or any standard noop). I like the idea of being able to quickly and easily grep for these kinds of things, plus if we all use the same one, it's just a single closure/function being generated. obviously this isn't a big deal

[aduth]

I think it works well when we use noop from lodash (or any standard noop).

Yeah, I don't feel strongly either way, though I find it's nice to limit the dependencies, and this should become a common enough pattern for an empty function that I don't think it really harms readability.

[dmsnell]

@aduth I hope you don't mind the hit-and-run here, but I saw your PR without any comments and poked my head in. didn't see any concerning issues with the code but I left a couple comments. thanks for the work - the media system is really great IMHO

[aduth]

I hope you don't mind the hit-and-run here, but I saw your PR without any comments and poked my head in.

I'm always appreciative of your reviews 😃 Apologies for the delay in response, as I've been out for the past two weeks.

thanks for the work - the media system is really great IMHO

Thanks for the kind words!

[aduth]

Force pushed a rebase, including changing getButtons to getButtonSettings in 25f05a6.

Marking as ready to merge, though not planning to merge immediately.