Better aggregation support

Added support and tests for aggregation operations.
You mean something like this?

```
private boolean isPipelinesMissing(JsonArray pipelines) {
     return pipelines == null || pipelines.size() == 0; 
}
```
and
```
if (isPipelinesMissing(message.body().getArray("pipelines"))) {
        sendError(message,"no pipeline operations found");
        return;
}
```