Fixes #9. Edited Server.sendCommand method,
command to be stuffed must be surrounded in double quotes.
Additional logic added to Server.stop and Server.start methods.
Don't start a server that is already running, and don't stop a server that
is already stopped. Prevents multiple processes from being started accidentally.
Rename Server.getServerPIDs to Server.getPIDs
Rename Server.serverScheduler to Server.scheduler