[YDBOcto#382] Implement Date/Timestamp types

With YDBOcto#382 (closed), Dates and Timestamps are now available in Octo.

All Fileman Date fields are now classified to either DATE(FILEMAN) or TIMESTAMP(FILEMAN) based on the presence of "T" in %DT in the Input Transform.

See this page for detail on %DT: https://www.hardhats.org/fileman/pm/cl_dt1.htm.

Functions have been updated to accept date types as appropriate.