Expand the openinghour checker API

[veloxy]

Expand the checker API with some more useful checks such as:

• Getting the next opening hour/date base on given DateTime or now. eg getEarliestOpening(\DateTime $dateTime) : \DateTime
• Getting opening hours for certain date period (taking overrides into account). eg getOpeningHoursForPeriod(\DateTime $from, \DateTime $until) : array. Not sure of the format here yet.
• Check if open within given TimePeriod, eg: isOpenBetweenHours(\DateTime $date, TimePeriod $timePeriod) : bool
• ...

[veloxy]

Removing this from first release due to lack of time.