Allow manual adding of Javadoc and sources archives to existing artifacts

[UdoW]

Expected Behavior

Allow the manual adding of Javadoc and sources archives to existing JAR artifacts of the container "Project and External Dependencies".

For that: Go to project preferences under "Java Build Path". Select a JAR archive. Expand subtree and add Javadoc/source archive location to the given JAR archive. The selected Javadoc/source archive path is stored in the project preferences location somewhere in the .settings folder.

Context

There is a way to add the Eclipse preferences with the Gradle Eclipse plugin but this would need a change in the build.gradle which should be in my case independent of IDE specific stuff i.e. it should be not necessary to include the Gradle Eclipse plugin in the build configuration. Sometimes you do not have access to change the build.gradle, either.