[MNGSITE-420] Improve DependencyManagement Documentation

**[Ian Lavallee](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=ilavallee)** opened **[MNGSITE-420](https://issues.apache.org/jira/browse/MNGSITE-420?redirect=false)** and commented

An old test for the verbose dependency:tree has the following line:
+- org.apache.maven:maven-profile:jar:2.0.4:test (scope not updated to compile)

The documentation for the dependency management and dependency:tree both don't mention why this is displayed or why it occurs. My best guess is because the dependency management manages that artifact but the artifact is not transitive it is directly declared so the dependencymanagement doesn't affect it?

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No further details from [MNGSITE-420](https://issues.apache.org/jira/browse/MNGSITE-420?redirect=false)

Start with the old verbose dependency:tree test referenced in the issue, then read the dependency management and dependency:tree documentation. Clarify why the displayed scope is not updated and document the behavior in both relevant documentation areas.

Written by the indexing model from the issue text.