Return leading image for {{content words="0"}}

Closes #3884
- This PR includes a reimplementation of Downsize@0.0.5 with `words: "0"`. It uses the same parsing methods, therefore guarunteeing identical behavior.
- Tests have been updated to be more extensive.
First pass refactor of GUI readme redux
Merge pull request #3903 from JohnONolan/gui-readme

First pass refactor of GUI readme redux
Merge pull request #3888 from felixrieseberg/iss3884-content

Return leading image for {{content words="0"}}
Add alternative names for pg

refs #3864
- map alternative valid pg names to pg
Resets the scroll position on controller content change

When scrolling through the preview of a long article, if the
post was changed the scroll position of the preview would
remain the same.
Fix user cover images

No issue

The cover image method in the settings/user controller returned the correct asset URL, but not the corresponding CSS which is needed to show it correctly.
Merge pull request #3914 from halfdan/3864-db-config

Add alternative names for pg
Merge pull request #3819 from studioromeo/reset-preview-scroll-position

Reset preview scroll position when post item is clicked
Merge pull request #3934 from PaulAdamDavis/fix-cover-image

Fix user cover images
Remove permissions from configuration API

closes #3909
- Remove permissions from configuration API
- Remove permission setup from integration test
- Remove permissions from permissions.json
Update About page styles

Closes #3919

With the move to new global styles, the about page styles got a bit borked. This fixes those.
Merge pull request #3912 from halfdan/3909-config-api

Remove permissions from configuration API
Implement About Ghost page

Closes #3568
- Deleted html placeholders in client
- Added new grunt task, buildAboutPage, which 1)creates -contributors.hbs partial and 2) downloads contributor avatars
- buildAboutPage is called by anything that does an emberTemplates task
- Removed unused code from ghostpaths
Merge pull request #3907 from PaulAdamDavis/fix-about-styles

Update About page styles
Merge pull request #3575 from novaugust/about-ghost

About ghost page
Static integration of the new PSM

Reference #3932

Take this, and make it work.
Enlarge mobile matchMedia max-width

Closes #3941

It now matches the mobile MQ in CSS - https://github.com/TryGhost/Ghost/blob/master/core/client/assets/sass/components/navigation.scss#L163
Merge pull request #3935 from PaulAdamDavis/new-psm

[WIP] New post settings menu
Delete revoked tokens

closes #3758
- new API method to delete access and refresh token
- use new ember-simple-auth config to revoke tokens on logout
- new method to delete tokens by .. token