Ilrt.contentmigrator

- Add conversion of old links to archetype links.

[Ed Crewe]

- Bug fixes of utils AT types conversion methods -
setting empty dates to current date (hence expiring most content!)
and lines fields not converted correctly to tuples.

[Ed Crewe]

- Contains stand alone ContentMigrator product for exporting content
from old plone sites
- Uses generic setup style exportimport/content for importing content
- Imports file and image content
- Sets workflow state of content (requires ilrt.migrationtool)
- Imports users, groups and roles
- Translates old calendar item type to ATEvent

[Ed Crewe]

- Initial package structure.

[zopeskel]