Crono plan: previous and next buttons should be in sync with period selector

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When clicking on the previous/next buttons on the crono plan, the calendar always move in one day. Instead, it should take into consideration what period type is selected:

• If day, continue as it is today
• If week, add 7 days
• If month, add 1 to the month (and take care of months with 28-31 days)
• If quarter, add 3 months as above?