Add actual plugin package

[daniel-beck]

Many plugin developers started putting their classes directly in io.jenkins.plugins.

Even if the archetype is not flexible enough to create a real package based on the plugin name, a placeholder io.jenkins.plugins.TODO package should be added.

[timja]

There’s a groovy file run at the end where you can do anything you want in it if the standard tools aren’t enough

[jglick]

archetypes/hello-world/src/main/resources/META-INF/maven/archetype-metadata.xml

Line 12 in 4000310

<defaultValue>io.jenkins.plugins.sample</defaultValue>

could be edited. Looks like empty-plugin lacks even that. I think we could do better without any tricks, though a Groovy postscript could perhaps fine-tune behavior.