Fix 403 errors after signup

Closes #2819

- Keep around the _csrfSecret on the session after regenerating
Clean up routes. Use new slug endpoint in admin.

refs #2814
-removed route /posts/slug/:title due to API change
-changed admin to use new slug endpoint
-removed duplicate notifications routes
Update Ember Components with proper gh- prefix

GH-ISSUE 2373
Ember Data with Posts

Ref #2699

- Introduce ember data dependency
- Add loadInitializers and refactor most initializers into one combined
- Add Post ember data model
- Refactor generateSlug to use title of post and ghostPaths
- Refactor post controller to not reference model.property everywhere
- Use RESTAdapter for posts, users and tags
- Setup author and tag relations in Post model
- Fix broken API calls by adding CSRF header
- Add initiaizer for csrf value
- Use actual User model for current user initializer
- Add action for setting featured post, test with actual api call
- Fix the sending of UUID's up to the server
- Refactor current-user to use ember-data store
- If a user is preloaded in the application, use pushPayload to put it
in the store
- Do a lookup on the store to get an actual User model for injection
- Fix posts/post controllerName in route/new.js
- Alter signup process to push user into ember data store
Merge pull request #2826 from jaswilli/route-cleanup

Clean up routes. Use new slug endpoint in admin.
Merge pull request #2718 from jgable/emberData

Ember Data with Posts
Merge pull request #2828 from lholmquist/GH-2373

Update Ember Components with proper gh- prefix
Merge pull request #2820 from jgable/fix403

Fix 403 errors after signup
Use new slug endpoint in ember admin

Closes #2831
-use new slug endpoint in fixture
-use new slug endpoint in post model
-do not try to generate slug for zero length titles
Merge pull request #2832 from jaswilli/issue-2831

Use new slug endpoint in ember admin
Merge pull request #1 from TryGhost/master

Sync with upstream