Unify the sending process after the best route is generated by the router

[saledjenic]

The Flow:

• a client requests from statusgo to build transactions for the best route that was displayed
• statusgo:
  • builds all transactions and sends signal to the client asking for signing transactions or
  • builds transactions one by one and sends to the client for signing, in the order which is determined by the router
• the client:
  • signs transactions and calls statusgo to send built transactions providing signatures for all of them or
  • signs transactions one by one and calls statusgo to send built transaction providing signature for it
• statusgo:
  • sends built transactions with received signatures
  • sends built transaction with received signature and waits for its execution before asking the client to sign next transaction
• once all transactions from the bundle are sent statusgo notifies client via signal that the multitransaction is sent