Server side maintenance improvements.
Add provider to maintenenace.
Add API endpoint for maintenance.
Add initial trivial permissions and test case for API.
	modified:   api/machine.py
	modified:   api/maintenance.py
	new file:   api/permissions.py
	modified:   api/serializers.py
	modified:   core/admin.py
	modified:   core/models/maintenance.py
Fix and update maintenance urls.
	modified:   atmosphere/urls.py
Add multi-cloud, multi-provider maintenance to the client side.
Add maintenance icon to provider and identity summaries.
Add conditional loading and selecting in router, identity summaries
and providers_menu.
Add instance_screen maintenance template. Display when user's selected
identity's provider is under maintenance.
Rework and respace some other surrounding javascript.
	modified:   resources/css/application.css
	modified:   resources/css/cloudfront.css
	new file:   resources/js/cf2/collections/maintenance.js
	new file:   resources/js/cf2/models/maintenance.js
	modified:   resources/js/cf2/router.js
	new file:   resources/js/cf2/templates/instance_screen/instance_screen_maint.html
	modified:   resources/js/cf2/views/instance_screen/instance_screen.js
	modified:   resources/js/cf2/views/main.js
	modified:   resources/js/cf2/views/settings_screen/identity_summary.js
	modified:   resources/js/cf2/views/sidebar/instance_list_item.js
	modified:   resources/js/cf2/views/sidebar/sidebar.js
	modified:   templates/application/login.html
	modified:   templates/cf2/index.html
Merge branch 'master' of github.com:iPlantCollaborativeOpenSource/atmosphere

Conflicts:
	api/maintenance.py