refactor file storage. All attachments are stored in the /files/PBEM directory, and passed by filename to storage helpers. NOTE: the Local storage mechanism provided by this plugin needs some attention.
Merge branch 'master' of https://github.com/habari-extras/pbem

Conflicts:
	pbem.plugin.php
All attachments are saved in /user/files/PBEM by default. Helper plugins are fed an array of such attachments and may modify the post body as needed.