issue 28: adding user verification per admin command (#28)

hi @whimboo !

here's a patch for issue 28. I've run some quick tests on it, seems ok.
this could perhaps still be tidied up some, but it is far better than the code it replaces in the first patch.
I've added some error-checking and tweaked the adminhelp array to support all this.
hi @whimboo !
(not sure whether I need to include your userid here0

I've rewritten this, but I wonder, if it's better to check the length of the array here, wouldn't it also be better to check that in the earlier cases that require an argument?