Stopped correcting spelling mistakes

This is potentially a breaking change, but I think correcting spelling
mistakes is out of scope for nickel, and will always be done better by
dedicated software
Moved nlp_query_constants to nlp_query/constants

I think more things will be going into that directory soon
Moved nlp_query punctuation replacement out to i18n
Moved nlp_query unnecessary word replacement out to i18n
Moved nlp_query holidays word replacement out to i18n
Moved nlp_query day names out to i18n
Moved nlp_query month names out to i18n
Moved nlp_query numbers out to i18n
Moved nlp_query times out to i18n