[thredds] Building THREDDS with Java 9, support for THREDDS and NetCDF-Java on Java 9

[Ben Caradoc-Davies <ben@xxxxxxxxxxxx>]

THREDDS on master is built with Gradle 3.4.1, which fails to start with 
OpenJDK 9:

FAILURE: Build failed with an exception.
* What went wrong:
Could not determine java version from '9.0.1'.

Updating gradle/wrapper/gradle-wrapper.properties to 4.3.1 got Gradle to 
boot but there were errors.

Tested with openjdk-9-jdk 9.0.1+11-1 on debian/sid amd64.

- Are there plans to support building THREDDS with Java 9?

- Is Java 9 a supported platform for THREDDS?

- Is Java 9 a supported platform for NetCDF-Java?

Kind regards,

--
Ben Caradoc-Davies <ben@xxxxxxxxxxxx>
Director
Transient Software Limited <http://transient.nz/>
New Zealand