javaunohelper: Number parsing

Change-Id: Ie6856ea4c196479aef1ce00a7cf2709fea8b3e42
Reviewed-on: https://gerrit.libreoffice.org/10860
Reviewed-by: David Tardon <dtardon@redhat.com>
Tested-by: David Tardon <dtardon@redhat.com>