I'm making some more improvements to the ViewModel...

# tornadofx

[edvin]

I'm making some more improvements to the ViewModel to support different use cases for the Wizard. I'm also adding some nice boolean bindings to the Wizard so you can configure how the navigation buttons behave more easily. For example, if you use autocommit and want to only enable next when the current page is complete, you can say override val canGoNext = currentPageComplete etc.