[Oomph-Setup] Add jdt.ui configuration setup

[HannesWell]

What it does

Add jdt.ui configuration setup.
Additionally add a styled and drag&drop-able Oomph Configuration button to the main README.

Part of eclipse-platform/eclipse.platform.releng.aggregator#2430

This currently depends on #1707 respectively contains the changed proposed there!

Author checklist

• I have thoroughly tested my changes
• The change is following the coding conventions
• I have signed the Eclipse Contributor Agreement (ECA)

[HannesWell]

This currently depends on #1707 respectively contains the changed proposed there! Therefore I suggest to submit that first.

[HannesWell]

This currently depends on #1707 respectively contains the changed proposed there! Therefore I suggest to submit that first.

I have now refactored this PR to not depend on #1707 so this can be submitted immediately.

@jukzi or @iloveeclipse, could you please submit this as well? Thanks in advance.

[jukzi]

probably unrelated: baseline and build for org/eclipse/jdt/internal/ui/text/correction/QuickAssistProcessorUtil.class have different contents have never seen such build error before.

[HannesWell]

probably unrelated: baseline and build for org/eclipse/jdt/internal/ui/text/correction/QuickAssistProcessorUtil.class have different contents have never seen such build error before.

Yes this change should not have any effect on the compilation or build results at all.

[merks]

Definitely the setups are invisible to the build. Best to get this merged so we get the setups in a consistent state again.

[merks]

If we can just get this committed, the setup-archiver will be ultra-happy again:

[HannesWell]

Thank you Andrey for submitting!

The result again looks good and as expected:

The installer website for JDT UI looks also good:
https://www.eclipse.org/setups/installer/?url=https://raw.githubusercontent.com/eclipse-jdt/eclipse.jdt.ui/master/org.eclipse.jdt.ui.setup/JdtUIConfiguration.setup&show=true