LP#1740535: retrieve list of billing types

LP#1740535: retrieve list of billing types

This patch changes how the web staff client retrieves the list
of billing types available for use by the Bill Patron modal. PCRUD
permissions on config.billing_type don't quite match how the
the set of billing types available to a staff user used to work
in the XUL staff client, so this patch uses the
open-ils.circ.billing_type.ranged.retrieve.all method instead.

To test
-------
[1] Log in as a Circulators staff user (assuming stock data
    and permissions).
[2] Try the Bill Patron dialog in the web staff client; note that
    no billing types are accessible.
[3] Apply the patch and repeat step #2. This time, it should
    include the miscellaneous billing type.

Signed-off-by: Galen Charlton <gmc@equinoxinitiative.org>
Signed-off-by: Kathy Lussier <klussier@masslnc.org>