renderPortal additional hooks

Adding two new hooks to allow for a portal to be hidden instead of rendered and to be re-rendered if the plugin has determined that it would like the rendering to occur.

There may be questions about why I added the ability for the callback to return true to stop processing more callbacks. It was specifically for the case of re-rendering. If a plugin has determined that it would like the portal to be rendered then it doesn't matter what any other plugin has to say. The plugin in question can return true to stop processing any additional callbacks.