Bug 13545 - Add barcode image generator service

Bug 13545 - Add barcode image generator service

If we add a script to Koha that can be passed a barcode, we will be able
to easily embed item and patron barcodes into html printable slips and
notices. This can be very helpful for librarians, as it means scanning
an image instead of typing in the barcode manually.

This patch adds a barcode image generator that can be passed a barcode
and an optional type ( defaults to Code39, all GD::Barcode types should
work ). This image can be embedded in html slips and notices.
( e.g. <img src="/cgi-bin/koha/svc/barcode?barcode=<<items.barcode>>"></img> )

Test Plan:
1) Apply this patch
2) Browse to /cgi-bin/koha/svc/barcode?barcode=123456789 on your server
3) Note the barcode image

Signed-off-by: Brandon <brandon_h27@hotmail.com>
Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>