POC: Populate flavor's capabilities selection widget with flavor:compute_capabilities namespace

In the flavors screen we should be able to hit a button called ‘add extra_specs’ or ‘add extra attributes’ and it should pop up the capabilities selection widget. Once the widget is launched, it must be passed in the namespace for ‘flavors’ basically this restricts the number of sub-namespaces that the widget will allow you to edit. The only sub-space we’ll start out with is the ‘compute_capabilities’. The widget will call an API that should return the data in the capabilities.json file. The widget will then allow the user to select whatever processor capabilities he wants.
When the user pushes the ‘save’ button, the widget will call some code in the backend. This is what we call the provider for that namespace. This code should take the selections that the user made and then writ it into the flavors as ‘extra_specs’ using the format that the compute_capabilities filter can understand