[BUG] Orders|Trustlines|Balances: Allow ledger hash query parameter (RLJS-137)

There's also the schema validator option:

```javascript
validator = require('./lib/schema-validator.js')

validator.isValid('123456','Hash256')
// => false

validator.isValid('FD22E2A8D665A01711C0147173ECC0A32466BA976DE697E95197933311267BE8','Hash256')
// => true

```