[MNG-6357] Dependency order should be nearest first

[belingueres]

Save the artifacts temporarily in a Map ordered by tree depth, and only after finishing iterating over the dependency tree are the artifacts added to the collection in depth order.

Note: IT-core test needs to be added replacing IT 3813 which does not apply any longer for a maven version containing this change.

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[belingueres]

Please review this patch. Tested it and seems to solve:

• MCOMPILER-317
• https://github.com/mojohaus/exec-maven-plugin/issues/91

[rfscholte]

Looks good at first sight. This code deserves a unittest, that's better than relying on plugins. I don't think the unittest is too hard to write. I noticed you're not using diamond operators. Looking at the code it should be written with the new Map methods, but that requires Java 8. The moment that Maven will require Java 8 is getting closer

[michael-o]

@rfscholte We have more serious problems that introducing fancy Java 8 features.

[jmhodges]

The merge conflict is pretty straight-forward to fix (it's a simple collision in the pom.xml). Would love to see this go in! Happy to provide a new PR if that's preferable

[cowwoc]

Per https://maven.apache.org/download.cgi Maven 4.x requires JDK 8. What is needed to move this PR forward?