support custom meta and custom template data for ac.composite.done() issue #948

This PR tries to match the api of ac.done() and ac.composite.done() now that we don't accept passing params and other data into all children.

The new API will work like this:

```
ac.composite.done({
    "title" : "something"
}, {
    "view": {
        "name": "detail"
    },
    "assets": {
        "top": {
            "js": ["something.js"]
        }
    }
});
```

The old API is still supported, in which case this will also work:

```
ac.composite.done({
    "template:" {
        "title" : "something"
    }
});
```

but a warning will be issued to announce the deprecation.

TODO: 

* Update examples
* Update documentation