sort components when merging discovered components with hand-provided components #27

extension to #8
issue found while using the plugin on maven-core, when merging discovered component with hand provided https://github.com/apache/maven/blob/master/maven-core/src/main/resources/META-INF/plexus/components.xml

require a fix in XML merge algorithm https://github.com/codehaus-plexus/plexus-containers/tree/master/plexus-component-metadata/src/main/java/org/codehaus/plexus/metadata/merge