Bug 35087: Discount rate only accepts a point as decimal separator

Bug 35087: Discount rate only accepts a point as decimal separator

When a comma is used to define the discount rate of a vendor,
the data is not recorded (as NULL), it is however recorded if the
separator is a point.

Test plan:

1) Go to acqui module and edit a vendor
2) Set a discount rate with a comma as decimal separator
3) Edit again or request your database to see that there is no data
   saved
4) Do it again with a point as decimal and see it works
5) Apply this patch and reloard the build for the templates
 6) Repeat step 2 and see the warning to inform you that you must use a
    point

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Sonia <sonia.bouis@univ-lyon3.fr>
Signed-off-by: Olivier V <olivier.vezina@inLibro.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>