Elasticsearch does not start as a daemon

[jasontedor]

Due to the settings refactoring and the magical action-at-a-distance way that some settings like es.foreground are set via system properties, Elasticsearch does not currently start as a daemon (and thus as a service) when built from master:

$ ~/elasticsearch/elasticsearch-3.0.0-SNAPSHOT/bin/elasticsearch -d
$ Exception in thread "main" java.lang.IllegalArgumentException: unknown setting [foreground]
        at org.elasticsearch.common.settings.AbstractScopedSettings.validate(AbstractScopedSettings.java:227)
        at org.elasticsearch.common.settings.AbstractScopedSettings.validate(AbstractScopedSettings.java:216)
        at org.elasticsearch.common.settings.SettingsModule.configure(SettingsModule.java:60)
        at <<<guice>>>
        at org.elasticsearch.node.Node.<init>(Node.java:224)
        at org.elasticsearch.node.Node.<init>(Node.java:156)
        at org.elasticsearch.bootstrap.Bootstrap.setup(Bootstrap.java:188)
        at org.elasticsearch.bootstrap.Bootstrap.init(Bootstrap.java:294)
        at org.elasticsearch.bootstrap.Elasticsearch.main(Elasticsearch.java:37)
Refer to the log for complete error details.

Closes #11564