Imports of wclayer command

PathSynopsis
github.com/Microsoft/hcsshim
github.com/Microsoft/hcsshim/internal/appargsPackage appargs provides argument validation routines for use with github.com/urfave/cli.
github.com/urfave/cliPackage cli provides a minimal framework for creating and organizing command line Go applications.
path/filepathPackage filepath implements utility routines for manipulating filename paths in a way compatible with the target operating system-defined file paths.