Included additional form fields when adding/editing a channel

Hi @rcrichton. When you have a chance can you just review the additional form fields i added for the channels form. I am encountering one issue i need you help with. How should the "Properties" be captured? I see in the schema it is objects within an array. Currently if i supply a value for this the save does not work as its not supplied in the correct format.
I Know this isn't code that you wrote for this PR but maybe we should rename 'roles' to 'groups'. We have called groups on the user page.