Do not eagerly fetch relations in when finding all posts

fixes #4232
- do not fetch tags and fields relations in post.findAll()
Fix high latency autosave bug in editor.new

Closes #4400
- Added focusCursorAtEnd property to codemirror component, to set the cursor at document end on load. Used for posts that have been edited
- centralized codemirror init code in component
Fix invalid image helper URLs when using a subdir.

No Issue
- Strip sub-directory from image paths before passing to
  config.createUrl. Since images are stored with the sub-directory
  and createUrl builds a URL with the sub-directory the result
  would be a URL that contains the sub-directory twice.
Improve validation for user.website

closes #4444
- validate URL without protocol in server and client
- when saving url, add `http://` if the url doesn't have a protocol
Merge pull request #4465 from jaswilli/subdir-image-url

Fix invalid image helper URLs when using a subdir.
Merge pull request #4459 from novaugust/slow-save-errors#4400

Fix high latency autosave bug in editor.new
Merge pull request #4436 from mattiascibien/issue-4232

Do not eagerly fetch relations in when finding all posts
Merge pull request #4466 from VictorVation/url-validation

Improve validation for user.website
Merge branch 'master' of https://github.com/TryGhost/Ghost