Add display_field column to config.metabib_field

Add display_field column to config.metabib_field

The idea is to pull the XPath definitions and i18nized labels for
config.metabib_field entries into other contexts, to avoid duplicate /
conflicting defintions in different layers of the code. If display_field
is TRUE, then it is a signal that it could be usefully exposed to users.

Signed-off-by: Dan Scott <dscott@laurentian.ca>
Conflicts:
	Open-ILS/examples/fm_IDL.xml
	Open-ILS/src/sql/Pg/002.schema.config.sql
	Open-ILS/src/sql/Pg/950.data.seed-values.sql

Signed-off-by: Bill Erickson <berick@esilibrary.com>