Revert "[PLXCOMP-220] invalid default uid/gid values never override the base (even if the base is blank); extracted default/override attribute handling into a common abstract class"

This reverts commit 12a78a620c00fee7e898bc793daf69f50550ad46.
Revert "[maven-release-plugin] prepare for next development iteration"

This reverts commit 66cc53c97c827f18981ef0b95fd258ae815e64eb.
Revert "[maven-release-plugin] prepare release plexus-io-2.0.7"

This reverts commit b88e90f2238aecc0808ff97294335b702d8e7c11.