add a bool to the HashAndHeight struct;
can indicate "final". When the block market final comes in,
we don't enter wait state, but instead ask for headers.
when you don't get any headers, you wont need any blocks, and that
will assert the wait state.
To try uspv, do ./lnd -spv
The remote node is hardcoded in shell.go. If you aren't
running a full node on localhost, specify where to connect to.
Nearby nodes will be much faster but random testnet nodes on the
internet should also work.
