Update open_order to api v2

[Ludvaer]

Opening orders through api v1 seem to be disabled, so I looked up documentation and fixed the code for new api version, also I fixed examples in accordance with how my code works now, which is without signature2, so I removed signature2 calculation and output but left result as {"transaction_data": transaction_data} for better compatibility with existing code.

[Ludvaer]

Was concerned something was wrong with this pr but it just viewing open orders and prices required updating links too.