Planned Development #7: Integrate node-checking & selection algorithm

This is to ensure we do our best to stay connected to the best possible node.

Especially important on first use as we want the wizard to be very simple and avoid adding node-selection until wallet has been created and user is at Dashboard screen.

@sschiessl-bcp How easy would it be to port your node-selection code over?

This also solves the occasional hardcoded node failure as in #6.