Payload commission is calculated incorrectly on the Send screen

[norlin]

At this line, the payload comission is calculated incorrectly, thus after the transaction is send, a node tries to withdraw different ammount (significantly larger) and the transaction may fail here if there is no funds.

Test case:

1. Make a new wallet (0 BIPs balance)
2. Send a transaction with 0 BIP and some payload: Test payload
3. The app shows Transaction Fee as 1.0240
4. Send the transaction
5. Get an error about insufficient funds with required sum 3.4 BIP (instead of 1.0240 as expected)

Possible solutions:

1. Request the transaction fee from node
2. Duplicate payload fees calculation logic from the node's code