Java 11 compatibility

[drcrallen]

Java 11 is the next LTS for the JRE http://www.oracle.com/technetwork/java/javase/tech/eol-135779.html and is currently anticipated to be released sometime in September 2018. This ask is that, when available, Druid is compatible with running on the next long term supported java version.

[leventov]

Just for reference, #4907 should be fixed first