Parallelizing batched elasticsearch output, default level is 4
Make Elasticsearch version check smarter, fixes #753

The Elasticsearch version check now checks if the version of the ES cluster
is in a specific version range (currently: 1.3.2 <= cluster version <= 1.3.4).

Conflicts:
	graylog2-server/src/main/java/org/graylog2/initializers/IndexerSetupService.java
Adding necessary import.
Increase maximum supported ES version to 1.4.99

Conflicts:
	graylog2-server/src/main/java/org/graylog2/initializers/IndexerSetupService.java
Adding debug statement to check when batched ES output flushes.