Imported From: http://groups.google.com/group/in-portal-dev/browse_thread/thread/cc382e2d8c64a41a#
Starting with In-Portal 5.0.0 there is ability to create "theme.xml" file
under "_install" folder in theme. This file holds meta-information that is
used to interact with theme templates.
You can even create "_install" folder under each module sub folder in one
theme, e.g.
...