Fix player logs in for the first time

Wasn't properly tracking if players were new for some reason - should be
solid now!
Add a hidden option to unlimit stack sizes in the give command

An official version of this would be useful, but first a less stupid
name needs to found. Ideas?
Don't check data when not needed in find.blocks tag

EG, .find.blocks[fire] would fail because fire blocks always have a
datavalue... shouldn't be needed.
Also, missed diff from previous commit.