Change command interface

Up to you whether to accept it Coelho. I changed 'halt' to 'stop' in order to prevent accidental shutdown of some Linux systems, as was complained about on some of the threads. It also adds a command not recognized response when it isn't 'stop'.
Note: I only did this on one other repository, so the others would need to be changed.
Remove comment and add halt

Adds 'halt' to the request, so 'stop' and 'halt' both work. Changes .equals() to .equalsIgnoreCase().
Merge pull request #1 from boboman13/patch-1

Change command interface