Support `--testnet` and `-T`. Fixes https://github.com/ltonetwork/lto-cli/issues/48 Swap listing inbound and outbound associations and sponsorship. Fixes https://github.com/ltonetwork/lto-cli/issues/53 Show help for commands as default action. Fixes https://github.com/ltonetwork/lto-cli/issues/45 Gracefully handle missing seed and private key. Don't show traceback on an error. Fixes 43 Show unbonding and leasing balance. Fixes 49