DIP from Maildir AIP.

refs #5150

Squashed commit of the following:

commit 35916dbc8d9ee22754c38af0665f1520d201ba21
Author: Joseph Perry <joseph@artefactual.com>
Date:   Fri Jun 21 16:25:53 2013 -0700

    DIP from AIP with MAILDIR.

    refs #5150

commit 5c823a51f53d182b4927b63185d32ef4f11b7efa
Merge: f01f5fd e7f61f3
Author: Joseph Perry <joseph@artefactual.com>
Date:   Fri Jun 21 15:04:38 2013 -0700

    Merge branch 'master' into dev/issue-1843.1

commit f01f5fd8521ef38e8afe48de4bf4e0e8fab0ae97
Author: Joseph Perry <joseph@artefactual.com>
Date:   Thu Jun 20 15:47:21 2013 -0700

    Recognize maildir AIPs.

    refs #1843

commit 6debdb25fdf59810de817faae1397bd0fdd04894
Author: Joseph Perry <joseph@artefactual.com>
Date:   Thu Jun 20 14:51:15 2013 -0700

    Redo normalization

    refs #1843