LP#1850547: add views for PO and line item state labels

LP#1850547: add views for PO and line item state labels

This patch adds two new views, acq.po_state_label and
acq.li_state_label, to map from the state codes to human-friendly
labels in a way that allows the labels to be retrieved and
translated.

This patch also changes the fieldmapper label of the PO
and LI state column from "State" to "Status".

This patch includes contributions by Mike Rylander.

Signed-off-by: Galen Charlton <gmc@equinoxinitiative.org>
Signed-off-by: Mike Rylander <mrylander@gmail.com>
Signed-off-by: Galen Charlton <gmc@equinoxinitiative.org>