LP#1427287: database schema for storing MARC tag+subfield metadata

LP#1427287: database schema for storing MARC tag+subfield metadata

This patch defines several tables, views, and functions for
storing information about MARC tags and subfields recognized
by Evergreen:

Tables:

* config.marc_format:   list of MARC formats; at present, however,
                        only MARC21 is supported
* config.marc_field:    list of fields recognized by the Evergreen
                        database.
* config.marc_subfield: list of subfields recognized by Evergreen

Views:

* config.marc_field_for_ou
* config.marc_subfield_for_ou

These two views assist in the process of determining the set of
MARC fields and subfields are meant to be in force at a particular
OU.  These are generally not meant to be queried directly, in
favor of the config.ou_marc_{sub}fields() functions.

Functions:

* config.ou_marc_fields(marc_format, marc_record_type, ou)
* config.ou_marc_subfields(marc_format, marc_record_type, ou)

These functions return the authoritative set of fields or
subfields in force at a given OU.

Signed-off-by: Galen Charlton <gmc@esilibrary.com>