nlpsolver: Number parsing

Change-Id: I37a83b8e8c0f084ae175be5a5c58fc6b852e23a1
Reviewed-on: https://gerrit.libreoffice.org/10807
Reviewed-by: David Tardon <dtardon@redhat.com>
Tested-by: David Tardon <dtardon@redhat.com>