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
Adding bower dependencies to vendor directory
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