Add support for PodPress podcasts

A client wishes to move their WordPress site into Drupal, which includes a podcast site that uses PodPress. Instead of trying to get them to upgrade away from PodPress first, I went ahead and added code to import PodPress items into Drupal.

PodPress doesn't seem to store podcast files as attachments, instead it just gets the user to enter a file address for the audio file. To get around this I had to add instructions for the user to copy over the audio files into Drupal's files directory, and then enter the file prefix, e.g., sites/default/files/podcasts_to_import. Suggestions welcome for a better way to handle this. I'm new to this module's code.

There is also a dependency on file_entity for the function file_uri_to_object which I use to add the file field attachment. Should I copy the code for that function into wordpress_migrate to remove this dependency?

Patch forthcoming.