Add method to DateTools to get user timezone id
Fix repeated registration of custom SimpleModule in ServerObjectMapperProvider
Move metrics-jvm into graylog2-shared POM
Add lots of JVM-related metrics to MetricRegistry singleton

The Metrics library provides a lot of JVM-related metrics out of the box which
only have to be registered with the MetricRegistry.

See https://dropwizard.github.io/metrics/3.1.0/apidocs/com/codahale/metrics/jvm/package-summary.html for details

Fixes #759
Generate system notification if GC takes longer than threshold

Long garbage collection runs are usually an early signs of an unhealthy system.
This changeset generates an URGENT system notification of type "gc_too_long" for
the node which suffered the long GC run.

The user can configure the check interval (`gc_check_interval`, default: 1 minute)
and the threshold (`gc_warning_threshold`, default: 1 second) in graylog2.conf.

Fixes #760
Remove unused MetricsHost class
Do not add timestamp to assembly output when using release profile.
Remove obsolete build scripts. Use maven assembly.
Move checkstyle.xml into config/ directory.
Add @Nullable to alert condition ids, fixes #762

When an alert condition is created the given id is null, as mongodb will
generate one for it.
Stop the server process on dependency injection errors.

Otherwise the process would just hang and do nothing.
Update Version class in REST client
Use correct route to delete index. Fixes #960.
Increase maximum supported ES version to 1.4.99
Add config option to disable Elasticsearch version check
Fix handling of message level in GelfOutput
Change "level" attribute in GelfCodec to int

The SyslogCodec and GelfOutput classes expect the "level" attribute of a Message
to be an int.
Injecting RadioTransport in RadioProcessBufferProcessor.

Before this, a single RadioTransport instance was passed to the
RadioProcessBufferProcessor constructor during instantiation. So now
every processor has its own transport instead of a single one being
shared between all of them.

(cherry picked from commit e4009be7aa976b68fd0de45a54dbc244e5f88231)
(cherry picked from commit 7245052c08a5d45ee51b4db129085a484cde3621)
Adding blocking queue, batch push/pop, bumping versions.

(cherry picked from commit a69474c7118d51690fecdb046fc503b2680e1ddc)
(cherry picked from commit c5d2ea4a5fe0fc57e3593bfd193149c7dc427eb2)
Adding more AMQP configuration options to radio configuration file.

(cherry picked from commit 759750a832c8e8199f767beece1bb451d5b47c77)
(cherry picked from commit 421c72a5fc83fe3b767225b88d079fa52c73f3a8)

Conflicts:
	graylog2-radio/src/main/java/org/graylog2/radio/Configuration.java