Make the shadowJar multi-release.

[gbggrant]

Description

This PR changes the jar packaging to be multi-release. This addresses the issues surfaced with the upgrade to gkl 0.8.8

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Content

• Added or modified tests to cover changes and any new functionality
• Edited the README / documentation (if applicable)
• All tests passing on Travis

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[lbergelson]

This is unnecessary for the fix but seems like a fine addition...

[gbggrant]

Yes. I was inspired by your example.

[lbergelson]

Looks good

[lbergelson]

We could add the following test to the script section of build.gradle. It doesn't add very much time to the build.

 # build the docs and shadowJars
 - ./gradlew
 # run a non-trivial tool to be sure it doesn't explode
 - java -jar build/libs/picard.jar MarkDuplicates -I testdata/picard/sam/aligned_queryname_sorted.bam -O out.bam --METRICS_FILE out.metrics

[lbergelson]

@gbggrant I think we have to merge my other pr that fixes that doc problem on java 11 before running the complete ./gradle build is going to pass.

[lbergelson]

Sorry, try replacing ./gradlew with ./gradlew currentJar