Add ScriptableSeq and ScriptableMap.

- ScriptableSeq is a wrapper for scala.collection.Seq instances that allows
developers to interact with them like it was a native JavaScript array.
- ScriptableMap is a wrapper for scala.collection.Map instances that allows
developers to interact with them like it was a native JavaScript object.

No put and delete methods of JavaNativeObject are overridden so that only
immutables collections are supported.
Make ServerToHandle trait sealed.

When a trait is "sealed" all of its subclasses are declared within the same
file and that makes the set of subclasses finite which allows certain compiler
checks.
Remove unused emptyRoutingTable.
Fix a typo: def -> val.
Make RoutingTableBuilder convertible to Json.

Define Writes[RoutingTableBuilder] which implicitly converts a
RoutingTableBuilder instance to Json.
Add return type to the writes method of Writes[RoutingTableBuilder].

This fixes scalastyle errors.
Add MongoDB binary path for Windows.
Add SystemMetricsActor.

SystemMetricsActor connects to the JMX agent and gets system metrics such as
system load average.
Override configuration with mode specific cofiguration.
Just get from configuration instead of get with fallback value.

Because default fallback value is managed by application.conf, get with
hardcoded fallback value is redundunt.
Extract config files from Global.
Use different paths of mongodb and zookeeper per mode.