2-dimensional wavetable

It would be nice to have a table oscillator that takes an array of wavetables, which we can traverse in two dimensions:
1. We can control the phase of the table with a parameter called `phase`.
2. We can modulate across tables with a second parameter called `position`.

Both parameters would range from 0 to 1. The function definition would be:
```js
el.table2([props], phase, position)
```

The props would be:
| Name | Default | Type | Description |
| --- | --- | --- | --- |
| paths | [] | Array | The names of sample buffers in the VFS |