[Add] BaseGateway Document: send_order.orderid should be unique
[Add] BaseGateway Document: send_order.orderid should be unique

msincenselee/vnpy,andrewchenshx/vnpy,vnpy/vnpy,bigdig/vnpy,vnpy/vnpy,bigdig/vnpy,msincenselee/vnpy,msincenselee/vnpy,bigdig/vnpy,andrewchenshx/vnpy,andrewchenshx/vnpy,bigdig/vnpy,andrewchenshx/vnpy,andrewchenshx/vnpy,msincenselee/vnpy