More shortcut functions in node-side interfaces

For instance, right now control.py has to do this:

``` python
execnode.send({'target': 'core',
    'type': 'addhooks',
    'hooks': ['node_loaded']})
```

It'd be much nicer if it could use

``` python
execnode.addhooks('node_loaded')
```

Of course with an arbitrary number of arguments. Everything can remain perfectly backwards-compatible because `execnode.send()` will work as it does now.
