Java requisite

[OrangeDog]

On Debian (specifically Ubuntu 18.04.1) the postinstall of elasticsearch 6.x requires Java to be installed.
This formula doesn't manage this dependency.

See also https://github.com/saltstack-formulas/logstash-formula, which does.

[OrangeDog]

It should also add the appropriate JAVA_HOME to the sysconfig by default.

[OrangeDog]

Just noting that ES 7 now has its own bundled JVM