Commented Feature: Add Multiple Navigator Support [9]

This is a bit of brain dump about what has to happen for this to happen

* NavigationApplication should become a ContentControl, content can be Navigtor's (which will also need to become content controls)
* Journal needs to move into NavigationApplication, as there can only be one Journal for all Navigators (to support only one frame going back at once)
* Journal needs ability to pop last FOR frame, when restoring from tombstone there is no guarentee that the first navigator will have the last navigation. The tombstone replay of the last navigation for each frame must be order independent
* Navigator needs to expose default controller/action dependency properties

This will enable configuration which looks something like

<NavigationApplication>
<Navigator /> <!-- Default navigator, navigates to Home.Default and looks for a frame called DefaultFrame -->
<Navigator DefaultController="Home" DefaultAction="HeaderDefault" FrameName="HeaderFrame" />
</NavigationApplication>
Comments: This is very low priority and I probably will can the idea. I can't see the value in the feature really, not for the effort and added complexity to the codebase.