Removing all transmit functions, and have widgets emit events

Right now it works like this : 

```javascript
nxWidget.on('data', function(data) { 
    doWhateverWith(data)
})
```

But I think in the future it would be great to have more detailed events :

```javascript
nxWidget.on('moved', function(old, nw) {
    doWhateverWith(old)
    doWhateverAgainWith(nw)
})
```