Member Tg::Color::Predefined: Add automatic conversion between Predefined and 24 bit colors.
Member Tg::Command::up: Move to Tg::Key?
Member Tg::Command::down: Move to Tg::Key?
Member Tg::Command::forward: Move to Tg::Key?
Member Tg::Command::backward: Move to Tg::Key?
Class Tg::Terminal: Further refactor the API to be more Qt-like. We don't need getChar(), for example, the class could hold keyboard buffer locally and notify Screen when needed via a signal.
Member Tg::Layout::Grid: Improve description (and implementation... ;-))
Member Tg::Style::screenBackground: implement ;-)
Member Tg::Screen::size: Differentiate between Terminal size and size of screen reserved for application