Shell command 'EXECUTE' gracefully handles an empty line

Signed-off-by: Tim van Boxtel <tim@vanboxtel.ca>
Shell commands fail gracefully if no arguments are provided.

Signed-off-by: Tim van Boxtel <tim@vanboxtel.ca>
Clean up comment artifact
Merge pull request #225 from SunPowered/shell_fixes

Neotools Shell Improvements