The standard approach on Darwin is to keen applications running when the
window is closed. Clicking the apps icon again in the doc should bring
back the application window.
This changeset refactors things to handle this. It will keep Zap and lnd
running in the background when the main application window is closed.
Quitting the app will stop both the app and lnd.
Fix#586Fix#601
Use grpc.credentials.combineChannelCredentials to combine the ssl
credentials with the macaroons when initializing the lnd rcp client.
This avoids the need to pass the macaroon metadata throughout the
codebase.
Tom Kirkpatrick
Ben Woosley
Jack Mallers
João Almeida