Add a <stripType> option to unpack goals

When using unpack-dependencies with

<useSubDirectoryPerArtifact>true</useSubDirectoryPerArtifact>
<stripVersion>true</stripVersion>

dependencies will get unpacked in directories like ${outputDirectory}/some-artifactId-jar/. In other words, the artifact's type is always appended; AFAICT from the code, there is no way to unpack into a directory whose name is just the dependency's artifactId.

It would hence be nice to have a <stripType> configuration option to mirror <stripVersion> and <stripClassifier> (although the later option is also ignored on unpack-dependencies. A separate bug?).