CarouselView: Getting null exceptions after updating to v2.0

Hey @alexrainman

I finally upgraded to v2.0, thanks for the improvement but I am partially delighted because some of the improvements break our app.

The reasons are:

1. I am now getting a null exception when setting App.Current.MainPage = new Page();. In your Demo project I can see that it is in the ExtendButtonRenderer, where Element is null.

2. Local renderers are overriden by the ones added in v2.0. A major upset, because we have multiple local renderers for button, editor, entry, etc. that are used to customise the controls.