Change to sdk style for easy CI/CD

[jamesmontemagno]

[Edit (AP): Also removes all iOS Classic API support and unifies some whitespace inconsistencies.]

[patridge]

@jamesmontemagno Thank you for helping me get this converted. I'm finally getting around to building and testing all this locally.

While it isn't a huge problem, do you know if there is a fairly non-invasive way to avoid all the XML doc warnings?

…/src/PDRating/PDRatingView.cs(18,18): Warning CS1591: Missing XML comment for publicly visible type or member 'PDRatingView' (CS1591) (PDRating)

[jamesmontemagno]

Oh you would just want to turn off warnings i guess. or comment it :)