Add automatic non-interactive wallet unlock command

Created by: petabytestorage

Wallet unlock with SIA_WALLET_PASSWORD environment variable non-interactively

Addresses trello public road map feature

https://trello.com/c/yRFaIgLb/65-enable-the-wallet-to-unlock-at-startup-without-user-intervention-advanced-less-secure-feature-primarily-for-hosts

See attached manual transcripts before and after patch showing positive test results. notes-02.txt notes-01.txt