Help text for "address command" missing argument for "account"

**Version**
bclient v0.1.1

**Expected**
```
./bin/bwallet-cli --network="regtest"
...
$ account get [account-name]: Get account details.
$ address [account-name]: Derive new address.
$ change: Derive new change address.
...
```

**Actual**
```
./bin/bwallet-cli --network="regtest"
...
$ account get [account-name]: Get account details.
$ address: Derive new address.
$ change: Derive new change address.
...
```
**Reproduce**

Does not work:
```
./bin/bwallet-cli --network="regtest" address
```
Works:
```
./bin/bwallet-cli --network="regtest" address "default"
```

Start with the help-text definition used by bin/bwallet-cli for the address command. Compare its displayed usage with the documented account argument, then run the regtest address commands shown in the issue and verify that help reports the argument and the command behavior remains correct.

Written by the indexing model from the issue text.