Pan and Zooming Behavior

Based on the discussion [here](https://github.com/esnet/react-timeseries-charts/pull/252#discussion_r202898021), #297 and PR #299 and giving it some thought, here's what we're thinking of doing.

Currently, we have a prop `enableDragZoom` which enables the ability to `drag to zoom + zoom using scroll wheel`. Also, there is another prop `enablePanZoom` which enables the ability to `pan and zoom`. It is a bit confusing and doesn't give you an option to customize what you're trying to achieve.

The alternative to this is suggested below. It will be a breaking change

**Alternative Props**

```
mouseDrag = none | zoom | pan
mouseWheel = none | zoom
```

**Backward compatibility**

```
enablePanZoom = {
mouseDrag: pan,
mouseWheel: zoom
}
enableDragZoom = {
mouseDrag: zoom,
mouseWheel: zoom
}
```

cc: @iabw @sb8244 @abramjstamper