Release 4.0

What's new:

1) Added work with non-custodial wallets

2) Added new transaction type - External Call. External calls are the calls that you make from your smart contract to another smart contract.

3) Added reduction of all balances to BTC

Improved/Fixed:

1) Added network type for tokens on Transactions/Wallets/Checkouts
2) Swap improvement
3) Checkouts improvements
4) Various bug fixes and improvements that improve system performance