Add `enabled` parameter to /v1/order

I found the parameter here: https://github.com/isocket/nodeapi/blob/aadf8a410411b874012c94730115ac63a9f3d5ed/server/routes/order.coffee#L78-81

Not sure whether this still exists or not, but it'd be nice to have a field to indicate whether an order is paused or not in the API.

@nhanphan @cloudezero thoughts?