Snooker API dates

Days, windows and how close a date is.

All dates and times are UTC. A match has date when the day it was played is known. Where it is not, played_between gives the window of days and date_known_to says how close that is:

• day: the day itself.
• round: the days its round was played.
• stage: the days of the main stage or of qualifying.
• event: the event's days.
• month: the month, for events dated only to a month.

Filter by days with from and to on GET /v1/matches: a match counts when its window touches them.