`Install SDK` is easy to miss

[stevemessick]

The Install SDK button on the new package wizard is easy to miss, at least in Android Studio. We should find a way to make it more discoverable. In the IntelliJ version of the wizard it is probably easier to see since the only topic on the first page of the wizard is the location of the SDK. (And so what I used to think is a bug turns out to be a feature :)

[stevemessick]

@devoncarew @pq
For Android Studio (only), I'm thinking we can improve this by adding an optional page at the top of the stack that only appears when no SDK is configured. If the SDK is set then everything stays as it is now. For first-time installations, before starting to create a project the user will need to download the SDK.