Fix max filename size report by FAT statfs with long file names; Add missing...

Fix max filename size report by FAT statfs with long file names; Add missing logic to support fieldwidth and justification for %s format; Add extended help options.  Default help command just shows a short list of commands.  Verbose and single command help options

git-svn-id: https://nuttx.svn.sourceforge.net/svnroot/nuttx/trunk@5008 7fd9a85b-ad96-42d3-883c-3090e2eb8679