And consolidate descriptions into lightning-feerates().
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Changelog-Added: JSON-RPC: `close`, `fundchannel`, `fundpsbt`, `multifundchannel`, `multiwithdraw`, `txprepare`, `upgradewallet`, `withdraw` now allow "minimum" and NN"blocks" as `feerate` (`feerange` for `close`).
v2 opens require you to use native segwit inputs
Changelog-Added: JSONRPC: `upgradewallet` command, sweeps all p2sh-wrapped outputs to a native segwit output