[ecash-wallet] Accept addresses in the transaction ouputs

Summary: This avoids pulling the ecashaddrjs lib or the ecash-lib when using the wallet for simple transactions.

Test Plan:

npm test

Reviewers: #bitcoin_abc, bytesofman

Reviewed By: #bitcoin_abc, bytesofman

Subscribers: bytesofman

Differential Revision: https://reviews.bitcoinabc.org/D18398