echo - add input verificaiton.
help - prints out commands in sorted order.
touch - add comments.
type - add error when file not found. add comments.
main lib files:
add comments, clarify error messages.
git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@11427 6f19259b-4bc3-4df7-8a09-765794883524