DotMake.CommandLine v2.0.0

• Updated to latest daily build 2.0.0-beta5.25174.1 of System.CommandLine.
• Fixed: On Unix-like platforms, Console.ForegroundColor and Console.BackgroundColor is unset/unknown so prevent setting them to
  ConsoleColor.Gray and ConsoleColor.Black on non-Windows platforms when theme color is null (unset).
  Also will try to fix color visibility by making some assumptions (e.g. on OSX background color is white)
  as it's impossible to detect terminal colors.
• Added: NO_COLOR support, i.e. if NO_COLOR environment variable is set, the colors will be disabled.
• Improved: Added CustomizeLayout method in CliHelpBuilder to mimic the base class HelpBuilder in System.Commandline.
  A delegate can be passed to customize the default layout sections in help output.
• Fixed: System.CommandLine.RootCommand returned by Cli.GetConfiguration should have correct parents. This did not
  effect the working of Cli, however for metadata purpose we will populate accurate command hierarchy even if
  Cli.GetConfiguration is called for a command which is in the middle of the hierarchy.