Fix bug calculating hasItemDatesParsed

[nonword]

Fix bug calculating hasItemDates (the property that controls whether or not the Date Filter is shown in RC):

• Favor numItemsTotal over numItems (which is not written by RCI)
• Don't assume that if numItems is not set, then numItemsTotal is set. There may be very old bibs that have neither
• Make the check greater-than-OR-EQUAL so that a bib that exactly meets the threshold gets a date filter
• Adds serializer tests