more work on new batched elasticsearch output which blocks.

* fixed some NPEs around missing remote addresses
* added a local file input type for benchmarking (this will be removed or hidden in the final version)
* new blocking ES output org.graylog2.outputs.BlockingBatchedESOutput
* initial information for throttling inputs via eventbus
* clear out processed raw messages more aggressively to have them garbage collected earlier
fixup license headers