To create a new interaction plugin, you must subclass the two classes in lib.php
and create the following entry points:

index.php?group=x - lists all instances in the given group
view.php?id=x display page for one instance.

The following strings are contract strings for an interaction plugin:
(example from forum)

$string['name'] = 'Forum';
$string['nameplural'] = 'Forums';
$string['addtitle'] = 'Add forum';
$string['edittitle'] = 'Edit forum';

