Breaking up methods in data import module

This implementation is inflexible, and should be broken
into smaller methods.  As a first start, this commit adds
a 'dry run' feature that dumps the data to stdout rather than
sending it to the Solr index.

Eventually, this will allow users to save import data in the form
it is indexed.  In addition, there will be a more flexible mapping
logic that the one-to-one arrangment here.
Major refactor: dates now ISO8601 timestamps

This is a big set of conditionals designed to get the "date"
field in Solr to serve as the basis for a date_sort field.

For good sorting on the current field (a TextField, not DateTime)
dates of the YYYY-MM-DDTHH:MM:SSZ kind are useful.  Where possible,
the importer transforms dc:date fields into this kind of string, adding
a copy of the original to :pub_date, to be used for display.

TO DO: reconfigure CatalogController's Blacklight configuration to
take advantage of this.  Date sorting should be on :date from now on,
and the date_query_facet_field should be scrutinized to ensure its
behavior is consistent with other features on the site.

More important TO DO: write tests for this!!

Also: remove copyField directive that copies :date to :pub_date, as
you will raise index-time errors if you try to write to a copy field.

Once we are confident we are only putting ISO 8601 compliant timestamps
into the :date field, we can test re-typing that field as DateTime, or
creating a new copy field so typed.
updating data submodule