Add BIP70 support to the mobile wallet

[damascene]

BIP70 payment protocol is essential for accepting payments in crypto currencies. There are many POS systems that have moved to BIP70 and no longer accept the BIP21 or don't favor it.

Example:
Anypay
Bitpay
GoCrypto
BCH register app

For list of some wallet that have implemented BIP70 support:
https://support.bitpay.com/hc/en-us/articles/115005701523-Which-wallets-work-best-for-a-BitPay-payment-Which-wallets-are-compatible-