build: package as zip instead of jar

[ricellis]

Checklist

• Tick to sign-off your agreement to the Developer Certificate of Origin (DCO) 1.1
• Added tests for code changes or test/build only changes - build changes
• Updated the change log file (CHANGES.md|CHANGELOG.md) or test/build only changes - build changes, will document in release notes.
• Completed the PR template below:

Description

Package as a zip instead of an "uber jar".

Approach

The "uber jar" failed to include all content from bundled dependencies because of path clashes. It is better to packge a directory so the dependencies can remain in their own jars.

This is achieved by using the gradle distribution plugin and creating a zip file.

Schema & API Changes

• Change in installation method.

Security and Privacy

• "No change"

Testing

• N/A build or packaging only changes, but did verify new output content, signature and function.

Monitoring and Logging

• "No change"

[tomblench]

should include docs/ dir too

[ricellis]

Added docs in 97606e8