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