Imports of 6-licensediff command

PathSynopsis
fmtPackage fmt implements formatted I/O with functions analogous to C's printf and scanf.
github.com/spdx/tools-golang/licensediffPackage licensediff is used to generate a "diff" between the concluded licenses in two SPDX Packages, using the filename as the match point.
github.com/spdx/tools-golang/spdxlibPackage spdxlib contains convenience and utility functions for working with an SPDX document that has already been created in memory.
github.com/spdx/tools-golang/tvloader
osPackage os provides a platform-independent interface to operating system functionality.