The nested <dependencyDefault> element closely mirrors the <dependency> element specification.
It provides the ability to set url, artifact, properties, version for a dependency that matches on
{groupId, artifactId, type}. Url, artifact, and version will only override the dependency's values if
the dependency doesn't provide the value, and (in the case of url and artifact) the dependency
doesn't provide a version (url and artifact are assumed to be version-specific).
Properties will only be overwritten, and only in the case where the dependency
doesn't specify them.
Dependencies are validated after merging with defaults, since version is not required
on either <dependency> or <dependencyDefault> but is required between the two.
o Added component interface/default impl for injecting project defaults.
o Added unit and integration tests.
git-svn-id: https://svn.apache.org/repos/asf/maven/components/trunk@163323 13f79535-47bb-0310-9956-ffa450edef68
John Dennis Casey