Bug 415813 - Fail early when trying to install artifact/medata to itself

Made DefaultInstaller bail out with exception if source and destination of install operation are equal
Bug 416294 - Add transparent WebDAV support to HTTP transporter

Made HttpTransporter check for WebDAV-capable server and issue MKCOL requests as needed to create missing parent directories before the actual PUT
Improved API docs around DefaultArtifactType
Improved API docs for ArtifactType