Move Gutenberg to be under "Posts" menu

[jasmussen]

From Helen:

https://twitter.com/helenhousandi/status/892392061793599489

Long term our hope is for Gutenberg to be the new post page, which would solve this. As an interim step, to make it easier for people to test this plugin, should we remove the separate menu item, and simply make items under the major Posts menu?

I.e.:

Posts
  All Posts
  Add New
  Add New (Gutenberg)
  Gutenberg Demo
  Categories
  Tags

[hedgefield]

That would put it closer to where people go to make posts 👍 although perhaps a little less prominent, but probably proximity will balance out prominence.

[StaggerLeee]

Maybe to make all Posts hidden from public to start with.
Homepage widgets, queries, sliders, etc will show all Gutenberg Posts as latest by date on each "Publish/Save".

Something those testing Gutenberg on live site(s) do not like and want.

[karmatosed]

I think either what you have @jasmussen or directly under 'Posts'.

[melchoyce]

From today's chat, let's also consider doing the same under "Pages." (Maybe we can leave out the demo there, though, and only have the demo live under "Posts.")

[paaljoachim]

I would suggest something like this:
(Perhaps use the word Gutenberg instead of editor. But I think we also need to get used to using the word editor instead of Gutenberg...)

and

[westonruter]

See also #1797.

[jasmussen]

Given Gutenberg is now default, I'm closing this one.