Natively support Ivy repository format

This is just an example. I cannot get Archiva to purge the repository at all. Group id is "atmel", artifact id is "avrasm2" and version is "2.1.39.83".

Consumer repository-purge had an error when processing file /storage/archiva/data/continuous/atmel/avrasm2/2.1.39.83/ivy-2.1.39.83.xml:
Invalid path to Artifact: filename format is invalid, should start with artifactId as stated in path.