Implement worksheet lists (using Angular)
Merge branch 'AngularWorksheets' of https://github.com/javierluraschi/codalab into dev

Conflicts:
	codalab/apps/api/views.py
	codalab/apps/web/static/app/index.html
	codalab/apps/web/static/app/js/app.js
	codalab/apps/web/static/app/js/controllers/root.js
	codalab/apps/web/static/app/js/controllers/worksheet.js
	codalab/apps/web/static/app/js/controllers/worksheets.js
	codalab/apps/web/static/app/js/directives/setfocus.js
	codalab/apps/web/static/app/js/directives/shortcut.js
	codalab/apps/web/static/app/js/services/worksheetsapi.js
	codalab/apps/web/static/app/partials/worksheet.html
	codalab/apps/web/static/app/partials/worksheets.html
	codalab/apps/web/static/css/Main.css