Compiled script help commands not persisted

Robot.RegisterScript(IMMBotScript script) was adding help commands to
HelpCommands, which is a dynamically generated List.

Now using Robot.AddHelp instead (which takes a string[] instead of an
IEnumerable, so calling ToArray() - could change IMMBotScript interface,
but that would break compiled scripts elsewhere).
Merge pull request #82 from Spksh/master

Compiled script help commands not persisted