Match cluster name in rekick cluster API

Adds a url match for /api/clusterbyname/$cluster_name so that clusters can be rekicked by name.
What about

```python
params = {}
if 'id' in kwargs:
    params['pk'] = kwargs['id']
elif 'name' in kwargs:
    params['short_name__exact'] = kwargs['name']

cluster = models.Cluster.objects.get(**params)
```