The screen origin is at the lower-left, so offsets and translations increase rightwards and upwards, in contrast to iOS and Web contexts, where the coordinate system increases rightwards and downwards. Duplicated style layer property declarations to reflect this difference.
Reduced the likelihood that the developer might attempt to set textField to an NSTextField or UITextField, or textFont to an NSFont or UIFont, or textSize to a CGSize or NSSize, or circlePitchScale to a number (given iconScale).
Information for Style Authors is now two separate guides, one for iOS and one for macOS. Both are compiled from the same template. Added language about rotation, tilting, and printing.
