Bulk scripting support to RabbitMQ river
Added bulk scripting support to RabbitMQ river:

```sh
curl -XPUT 'localhost:9200/_river/my_river/_meta' -d '{
    "type" : "rabbitmq",
    "rabbitmq" : { },
    "bulk_script_filter" : {
        "script" : "mock_script",
        "script_lang" : "native"
    }
}'
```
Have a look at [Native (Java) Scripts](http://www.elasticsearch.org/guide/reference/modules/scripting/) documentation for how to declare a script.

Relative to #17.

Closes #18.
Moving log4j properties to xml file in tests
### Doc per doc scripting

You may also want to apply scripts document per document. It will only works for index or create operations.

To enable scripting use the following configuration options:

```sh
curl -XPUT 'localhost:9200/_river/my_river/_meta' -d '{
    "type" : "rabbitmq",
    "rabbitmq" : {
        ...
    },
    "index" : {
        ...
    },
    "script_filter" : {
        "script" : "ctx.type1.field1 += param1",
        "script_lang" : "mvel",
        "script_params" : {
          "param1" : 1
        }
    }
}'
```

* `script` is your javascript code if you use `mvel` scripts.
* `script_lang` is by default `mvel`.
* `script_params` are optional configuration arguments for the script.

The script will receive a variable called `ctx` which contains a String representation of the current document
meant to be indexed or created.

For more information see [Scripting module](http://www.elasticsearch.org/guide/reference/modules/scripting/)
Closes #26.
Assert failure in bulk message parsing not caught
The RabbitmqRiver class has a try/catch around the parsing of the task's body into a BulkRequest. If this request is malformed, then the BulkRequest.add() method could fail with an assertion failure. This is not caught by the Exception.

Changing this to a catch(Throwable) allows the consumer to ack the message and move on to the next one.
Closes #14.
Move to RabbitMQ client 3.1.1
Cleaning also a little pom.xml before release
Closes #27.
prepare release elasticsearch-river-rabbitmq-1.6.0
prepare for next development iteration