Added inputs/UArizona/maps/DwC.specimens.csv autogen maps

inputs/UArizona/maps/DwC.specimens.csv: Mapped more fields

mappings/DwC1-DwC2.specimens.csv: Remove date -> date/_alt/2 mappings because they prevent the original DwC2 date field from being mapped to without an extra /_alt/2 appended

xml_func.py: Use new dates.strtotime(). When component date parts specified, year defaults to dates.epoch.year.

dates.py: Added strtotime() to wrap dateutil.parser.parse() with default defaulting to epoch, so that e.g. months with day missing default to day 1 instead of the current day of the month

mappings/DwC1-DwC2.specimens.csv: Map eventDate,dateIdentified using /_alt/2 and year/month/day using /_alt/1 so that inputs with both a date and date parts will select between the two

input.Makefile: Added comment that self map must be made first if it's needed for maps/$(via).%.full.csv

Makefiles: Use .SECONDARY with no prerequisites instead of setting a .PRECIOUS for each intermediate, to simplify turning off automatic deletion of intermediate files

inputs/UArizona: Added initial maps/DwC.specimens.csv

DwC mappings: Map datasource name via institutionID to avoid conflicting with existing institutionCode fields that many DwC data sources have