Move query parser in its own mod

[Keats]

Another potentially controversial change but it feels cleaner to me, especially if a schema mod is created later, rather than prefixing files with schema_.

[tailhook]

Yes. Looks fine. That was also my plan. But I've planned to do it after SDL, as it may share some nodes (Value for example) with query language and it would be easier to find out better places for everything/