Update when.js dependency to version 3.2.3
Content screen: Featured posts

fixes #2748
- Properly handle marking post as featured/non-featured
- Show correct notifications
Implements page class toggling.

- Toggles page class when post is marked as static/non-static
Fix slug create and update logic for posts

-Remove unnecessary calls to the slug API endpoint on the
 content screen.
-Only make slug API endpoint calls in editor when the post is new.
-Improve logic for when to update the slug.
Fix csrfSecret handling

Closes #2974
-use req.session.csrfSecret instead of _csrfSecret.
-clear username and password properties from the signin controller.
Merge pull request #2968 from jaswilli/slugs

Fix slug create and update logic for posts
Show notification on successful sign out

Closes #2977
Merge pull request #2979 from jaswilli/issue-2977-signout

Show notification on successful sign out
Lazy load default settings

Closes #2061

- Lazy load the defaultSettings value in Settings model
- Populate individual defaults before read/edit
- Populate all defaults before first browse call
- Remove populateDefaults calls from init code
Merge pull request #2975 from jaswilli/csrf

Fix csrfSecret handling
Merge pull request #2969 from jaswilli/when

Update when.js dependency to version 3.2.3
Merge pull request #2980 from jgable/lazyLoadDefaultSettings

Lazy load default settings
Merge pull request #2972 from halfdan/2748-featured-post

Implement featured post / page
Ember Admin - Upload Modal

Issue #2547