The documentation about 'Registering Actions from Code' at
http://www.jetbrains.com/idea/plugins/action_system.html
explains how to register actions form within code, but it does not state in what code/class one would do the actual registration.
It would be very helpful if the documentation explained whether to register an action in an application component, or in a project component, or wherever it should be done (I don't know the answer).