Rename client -> clientold

issue #2271

- should allow development of new admin UI whilst still having access to the old ui
Merge pull request #2274 from ErisDS/ember-rename

Rename client -> clientold
Create base route for ember admin
Add basic template for Ghost admin in Ember

Inspired and derived from:

https://github.com/taras/Ghost/compare/ember-admin
https://github.com/manuelmitasch/ghost-admin-ember-demo
https://github.com/stefanpenner/ember-app-kit
Merge pull request #2269 from hswolff/ember-admin

Ember admin
Move Ember Admin to use es6 modules

- adds required dependencies to package.json
 and to bower.json
- added required Grunt tasks to transpile and
 concat ember admin files
Added directory structure
Merge pull request #2281 from taras/ember

Merged into ember and added directory structure
Fixed Hanlebars path in concat:dev task
Excluded all unnecesssary files from Bower managed packages
Update bower.json with dependencies.
Adding bower dependencies to vendor directory until bower setup is merged into ember branch.
add new bower dependencies to gruntfile
Add admin prototype from https://github.com/manuelmitasch/ghost-admin-ember-demo
Not working properly: added ic-ajax mock in app.js but promise not resolving => loading route always active
Fixed paths to showdown extension
Minor refactoring of the routers:
- Moved post route under posts resource
- Changed ajax to use ic.ajax.request instead of ic.ajax.raw
Change fixture response of posts route to actual format.
Adding assets (scss, fonts, img) and configuring grunt + middleware to use them.
Make code confirm to code style

* indentation 4 spaces
* export statement at the end
* trim trailing white spaces
Extracted classNames logic of routes into style-body mixin.

Additionally replaced all double-quotes with single-quotes for style conformance.
Add Sublime Text settings to .gitignore