to do for a first real version:
- link integrity vs iterate
- create method to re-create integrity refs for the whole site and
  integrate that into migration and the control panel
- what about ftp/dav?

nice things to have later on:
- use annotations in info adapter (info.py)
- update implementation notes
- it would be possible to cancel single removals while going through with
  the others, but only if a potentially uncaught (by other code, i.e. third
  party products) exception was raised on cancel;  atm it's unclear if this
  would be desirable, though...
- reintroduce objects names/path in portal message on cancel
- add warnings about moved images/pages
- factor out all archetypes related stuff using adapters etc (i.e. references)
- possibly replace atreferences by something more generic (five.intid should do)
- use pullparser.py instead of the newly written link-parser?