text: Title: per channel/content access control
  Body: Implement a general model **AccessControl** with roles_accepted definition for read/edit/list/delete
  
  This will be applied for Channel and Content
  
  This should have a default **api** method to check the permission
  
  The generic views and api should call this method to define if access is allowed.
  
  The admin should query the fields to define the access control.
  