CLI usability: make use of units (order creation, display of balances)

When submitting an order, you need to submit a balance as a multiple of 100,000 satoshis (which is a unit). However, the CLI still asks for satoshis, and also shows satoshis in other places where a unit would help (in addition to the satoshis). From a technical point of view this is no issue at all, as it is clear which value is expected. Furthermore, converting between units and satoshis is straightforward.

However, as a human being who uses the CLI, I'm quite sick of counting zeros, and finding the number I need to change in order to make my amount a whole unit. Please make it possible to submit an order by specifying the number of units.

Current:
```
pool orders submit ask 12200000 xxx --interest_rate_percent=0.5 --lease_duration_blocks=2016
```

Proposal:
```
pool orders submit ask --units 122 --acct_key xxx --interest_rate_percent=0.5 --lease_duration_blocks=2016
```

Start with the `pool orders submit` CLI entry point and review the other CLI locations that display balances. Confirm how unit values should coexist with satoshis, then verify that order creation accepts `--units` and that relevant balance displays include units without losing satoshi values.

Written by the indexing model from the issue text.