Instance Scoping

New in version 1.0 is the ability to quickly define different creation modes.  This functionality can be configured with the new optional "Scope" property on the [PluginFamily] attribute or the "Scope" attribute on the <PluginFamily> node.  The alternatives are:

1. PerRequest - The default operation.  A new instance will be created for each request.
2. Singleton - A single instance will be shared across all requests
3. ThreadLocal - A single instance will be created for each requesting thread.  Caches the instances with ThreadLocalStorage.
4. HttpContext - A single instance will be created for each HttpContext.  Caches the instances in the HttpContext.Items collection.
5. Hybrid - Uses HttpContext storage if it exists, otherwise uses ThreadLocal storage.