Added support for aliases to create index api

It is now possible to specify aliases during index creation:

```
curl -XPUT 'http://localhost:9200/test' -d '
{
    "aliases" : {
        "alias1" : {},
        "alias2" : {
            "filter" : { "term" : {"field":"value"}}
        }
    }
}'
```

Closes #4920