Cleanup naming & order in admin controller

no issue

 There seemed to be no convention or order to the functions in the admin controller, so I have:
 - organised them
 - reordered them
 - added a small doc-block
 - reordered some routes
 - updated tests accordingly
Rename client -> clientold

issue #2271

- should allow development of new admin UI whilst still having access to the old ui
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
Ember Admin UI with ES6 and Prototype by Manuel Mitasch

closes #2303
- adds required dependencies to package.json and to bower.json
- added required Grunt tasks to transpile and concat ember admin files
- 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.