datastore: _action_All methods removed.

(RE: #41)

`saveAll` -> `save`
`delAll` -> `delete`
`getAll` -> `get`

For `save`, it accepts either a single object, or an array of objects formatted like:

```js
{
  key: ['Kind', null],
  data: {
    arbitrary: 'value'
  }
}
```
Is executing the callback with the `err` object the right behavior, or should we do the usual "if (err) callback(err) else callback(null, response)" pattern?