iOS Unified API Support

This is a rather large PR, so let me summarize the changes:

**iOS Unified API Support**
- Changed types in source code (RectangleF becomes CGRect, etc.)
- Added #if __UNIFIED__ to retain Classic API support
- Added ZZZZZ-Classic.csproj for classic support - for samples and library

- Consolidated samples into one place (they were in two and seemed out of sync)
- Updated rakefile to package using the component.yaml component definition instead
- Updated xamarin-component.exe tooling to support new ios-unified target
- Cleaned up some unnecessary files that were in source control
- Updated component to 1.12 build