Support setting foreground/background colors to terminal defaults (#8073)
Support setting foreground/background colors to terminal defaults (#8073)

* Support setting foreground/background colors to terminal defaults

Adds fgDefault to ForegroundColor and bgDefault to BackgroundColor
enums.

For Windows console, the default foreground color is assumed to be
white, and the default background color black.

* Add default fg/bg color caching for Windows Console

dom96/Nim,dom96/Nim,dom96/Nim,dom96/Nim,dom96/Nim,dom96/Nim,dom96/Nim