Fix issue #894

[Zardoz89]

If <release> tag is present, ignores <source> and <target> tags. This allows to use <release> tag with a JDK >= 9

Additionally, shows on maven output, the Java release that would be using.

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[eric-milles]

Thanks for the bug and PR. A new groovy-eclipse-compiler artifact should be available shortly.

[Zardoz89]

I would keep getLogger().info(String.format("Compiling for Java %s release.", release )); as is usefull information when one use maven from console. But thanks for merging this.

[eric-milles]

If you add <verbose>true</verbose> to your compiler's <configuration> element, you can see all the command line options being passed to the batch compiler, not just the release setting.