Use new nash-rust http client for place_order and cancel_order

[notonamap]

Contents:

• move place_order and cancel_order to nash-rust http client because of timeouts on websockets
• upgrade to tokio 1.0 to be in sync with the new nash-rust version
• include Ethan's sign_states_loop Nash parameter
• remove a bit of legacy margin code from websockets
• order_status param as a filter for order history if supported

once this gets merged we can probably close these:

• Update to latest nash client which supports concurrent requests #153
• Upgrade tokio to 1.0 #156, Upgrade tokio to v1.0.1 #154

and on nash-rust:

• Upgrade tokio to v1.0 nash-rust#47, Upgrade tokio to v1.0 nash-rust#46